Consolidated contact lens molding

ABSTRACT

An automated method and apparatus is provided to mold, cure and package soft contact lenses. A conveyor system transports an array of molds through a plurality of automated work stations. The front curve mold halves are partially filled with a polymerizable monomer or monomer mixture and assembled and clamped to displace any excess hydrogel from the mold cavity. The assembly is precured and then transported through a cure station using UV radiation to complete polymerization, The assemblies are then pried apart in an automated station, with any excess monomer adhering to the removed mold half. The newly molded lens is then hydrated and separated from the front curve mold half in a hydration station. Following hydration the array of lens is automatically deposited into a plurality of packages with a robotic transfer device having a plurality of figures which transfer the lenses.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Ser. No. 09/005,277 filedJan. 9, 1998, now U.S. Pat. No. 6,039,899, which was a continuation ofU.S. Ser. No. 08/461,887, filed Jun. 5, 1995, now abandoned, which was adivisional of U.S. Ser. No. 08/258,654, filed Jun. 10, 1994, now U.S.Pat. No. 5,804,107, all of said applications being entitled“Consolidated Contact Lens Molding.”

1. FIELD OF THE INVENTION

The present invention relates generally to the field of manufacturingophthalmic lenses, especially molded, hydrophilic contact lenses, andmore specifically, to a high speed, automated contact lens moldingsystem for automatically producing ophthalmic lenses.

2. DESCRIPTION OF THE PRIOR ART

The direct molding of hydrogel contact lenses is disclosed in U.S. Pat.No. 4,495,313 to Larsen, U.S. Pat. No. 4,565,348 to Larsen, U.S. Pat.No. 4,640,489 to Larsen et al., U.S. Pat. No. 4,680,336 to Larsen etal., U.S. Pat. No. 4,889,664 to Larsen et al., and U.S. Pat. No.5,039,459 to Larsen et al., all of which are assigned to the assignee ofthe present invention. These references disclose a contact lensproduction process wherein each lens is formed by sandwiching a monomerbetween back curve (upper) and front curve (lower) mold sections carriedin a 2×4 mold array. The monomer is polymerized, thus forming a lens,which is then removed from the mold sections and further treated in ahydration bath and packaged for consumer use. Hydration and release fromthe mold of this type of lens is disclosed in U.S. Pat. No. 5,094,609 toLarsen, and U.S. Pat. No. 5,080,839 to Larsen, both of which areassigned to the assignee of the present invention.

At the present time, partially automated and semi-automated processesare used in the production of soft contact lenses, however, highproduction rates are not achievable, partly due to the strict processcontrols and tight tolerances necessary in the production of highquality contact lenses.

Typically, the molds for these lenses are formed, generally by injectionmolding, from a suitable thermoplastic, and the molds, usually in framesassociating a number of such molds with support structure are shippedfrom a remote molding facility and stored for use in a productionfacility for manufacturing contact lens blanks.

It is known that the use of lens molds maintained under normalatmospheric conditions leads to inhibition of, and thus incomplete andnon-homogenous curing of the reactive monomer composition at the surfaceof the lens, which in turn can adversely alter physical properties ofthe lens. This phenomenon has been traced to the presence of oxygenmolecules in and on the lens mold surface, which is due to its inherentcapability of the preferred polystyrene molding material to sorbquantities of oxygen. During molding, this oxygen can be released to thepolymerization interface with the reactive monomer composition inamounts which exceed acceptable maximums as determined by empiricaltesting. More specifically, the oxygen copolymerizes rapidly with thereactive monomer but the polymerization chain thus formed is readilyterminated, the result being a decrease in rate of monomer reaction, thekinetic chain length, and the polymer molecular weight. The criticalityof oxygen level and the difficulty of implementing effective controlprotocols may be appreciated by recognizing that the level of oxygen atthe reactive monomer/mold interface must be controlled to approximately300 times less than the concentration of oxygen in air (3×10⁻³moles/liter).

This recognized problem has been addressed in the art by careful buttime consuming and laborious preconditioning of the molds utilizingchambers evacuated to approximately 1 torr and maintained in thiscondition for a period of not less than 6-12 hours. Any interruption ofthe work cycle such as might be caused by a power interruption requiresreinitiation of the conditioning treatment.

Even brief exposure of the molds to air after degassing, as in normalmanufacturing handling is detrimental; it has been learned that even aone minute exposure to air results in sufficient absorption of oxygen torequire 5 hours degassing to reacquire an acceptable condition.Accordingly, a degassing operation immediately proximate themanufacturing line, particularly for large volume transfers of moldswith different exposure times was deemed impractical, and no realimprovement over the present system.

The problem is complicated by the fact that the front and back curves ofthe juxtaposed mold sections exhibit different thicknesses, leading topotentially different exposure of the reactive monomer composition tooxygen across the surfaces of varying cross-sections which could resultin distortion of the lens and degradation of its optical properties.Thus, the concentration distribution of oxygen in the respective moldsections or halves remains symmetrical for short degas times, butbecomes progressively less symmetrical for longer degas times, and theanomaly can cause uneven cure and different properties between the frontand rear surface. For example, the convex male mold may be degassedwithin about 2 hours, whereas the concave female mold may not beentirely degassed even after 10 hours.

The commercial demand for soft contact lenses has dictated thedevelopment of continuous or at least semicontinuous manufacturinglines. The criticality of manufacturing specifications in turn demandsautomated handling of the lens manufacturing operation.

Another problem specific to the production process used to producecontact lenses in accordance with the teachings of the foregoing patentsis that the mold portions are surrounded by a flange, and the monomer ormonomer mixture is supplied in excess to front mold curve prior to themating of the mold halves. After the mold halves are placed together todefine the mold cavity, the mold is weighted and the excess monomer ormonomer mixture is expelled from the mold cavity into the space betweenthe flanges. Upon polymerization, this excess monomer or monomer mixtureforms a waste by product known in the art as a HEMA ring (whenhydroxyethylmethacrylate monomer is used) which must be removed to avoidcontaminating the production line or the packaged lenses.

In these prior art processes, corona discharge devices are at timesutilized to create an adhesion zone on the underside of the back curvemold half, to thereby cause the HEMA ring to preferentially adhere tothe back curve at the time the mold haves are separated.

The prior art process for separating the mold halves and removing thelens consists of preheating, heating, prying and removal. Hot airprovides the heating, mechanical leverage the prying, and the removal ofthe HEMA ring is manual. Heating the mold by convection is not anefficient heat transfer technique. From the time a mold array enters theheating apparatus until the back curve mold half is completely removedrequires on the order of one minute.

The present method for removing the lens is to apply heat to the backcurve mold half by means of a heated air stream. The heating is done intwo stages: a preheat stage and a heat/pry stage. In the heat/pry stage,the mold is clamped in place and pry fingers are inserted under one sideof the back curve of the mold, and an upward pry force is applied duringthe heating cycle. When the required temperature has been reached, theback curve mold portion breaks free and one end is lifted by the pryfinger and the mold half is removed. The remaining mold and lens is thenremoved from the heating and prying station, where remnants of the HEMAring are removed manually. The temperature gradient achieved in theconvection heating of the lens is relatively small, since the time ittakes to heat the back curve mold half enables significant conductiveheating of the lens, thereby decreasing the gradient, and makingseparation of the molds difficult. Adding more heat to the lens mold atseparation only causes the back curve mold to soften and impairefficient mechanical removal. Finally, manual removal of the remnants ofthe HEMA ring is labor intensive and costly.

While the aforesaid production processes have some efficacy in theproduction of soft contact lenses they suffer a number of disadvantageswhich have hindered the development of a high speed automated productionline. When mold frames are demolded in large batch processes, a poweroutage at the wrong time can effectively shut the entire production linedown for many hours after restoration of power, while a batch of framesis degassed and readied for production. In the alternative, expensivecontrol systems are required to protect partially degassed frames duringa power outage.

Further, the use of large mold arrays can cause registration problemsfor precision automated machinery if the polystyrene frame is distortedin any way.

SUMMARY OF THE INVENTION

The invention involves the improved manufacture of lens blanks for softcontact lenses and more particularly to subsystem stations, operations,procedures and protocols implemented in a continuous or at leastsemi-continuous automated manufacturing line to provide high speed, highvolume production with a reduced number of defective lenses or lenses ofimpaired physical or optical characteristics.

The invention includes a method implemented by associated apparatusaccording to a protocol to control oxygen levels at the interfacebetween the lens mold blank and the reactive monomer composition withinlevels for reliable production of lenses of acceptable optical qualityunder optimum manufacturing conditions, thereby substantially reducingdefect levels.

It is therefore an object of the present invention to greatly minimizethe exposure of the monomer or monomer mixture to atmosphericconditions, particularly oxygen, and to reduce the amount of dissolvedoxygen in the monomer or monomer mixture used to produce the lenses.

It is also an object of the present invention to incorporate acompletely automated production line system for automaticallytransporting contact lens mold portions throughout the contact lensfilling, precuring, polymerizing, and demolding stations in a fast,efficient and precise manner.

Another object of the present invention is to provide a high speedapparatus for removing fragile front and back curve mold halves from amold in which those articles are made, and then transporting thosehalves to and depositing those halves in a high speed, automatedmanufacturing system, in a low O₂ environment.

A further object of this invention is to transport polystyrene moldhalves from a mold in which those halves are made, and into a low oxygenenvironment of an automated contact lens molding system, in less than 15seconds.

These and other objectives are attained with an apparatus for removingand transporting the mold halves from a mold, in which they are moldedin an essentially oxygen free environment and transferred to theautomated production line by robotic apparatus generally comprisingfirst, second, and third robots or assemblies. The first assemblyremoves the mold halves from the mold and transports them to a firstlocation, the second assembly receives the mold halves from the firstassembly and transports them to a second location, and the thirdassembly receives the mold articles from the second assembly andtransports the articles to a third location on pallets for entry intothe automated line, while protecting the optical surface and whererequired, flipping the curve, for most efficient down stream processing.

It is still another object of the present invention to incorporate in anautomated contact lens production line facility, an automated palletsystem wherein a carrier pallet is provided that can receive both frontcurve lens mold portions and back curve lens mold portions prior to theformation of a lens mold assembly.

Specifically, the contact lens pallet system comprises a pallet forcarrying and protecting the optical surface of one or more contact lensmold assemblies throughout an automated contact lens production line,the pallet having one or more first recesses formed in a surface thereoffor receiving an individual contact lens mold assembly, the contact lensmold assembly comprising a first front curve mold half and acomplementary second back curve mold half.

It is an object of the present invention to provide an apparatus forfilling and assembling mold halves for a contact lens which includes afirst automated station for receiving a plurality of front curve contactlens mold halves, carried in a unique pallet carrier, which are thenfilled with a predetermined amount of a polymerizable monomer or monomermixture. The apparatus also includes a second automated station whichprovides a coating of surfactant on a portion of the front curve lensmold part to provide for preferential adhesion of any excess hydrogel toa back curve mold part. The apparatus further includes a third automatedstation for sequentially receiving a plurality of back curve mold parts,removing the back curve mold parts from the carrier pallet, and thenreceiving and registering the back curve mold parts with a plurality offront curve mold parts which were previously filled with thepolymerizable monomer or monomer mixture. A vacuum is first drawn aboutthe mold parts, and then the back curve is assembled with the frontcurve and weighted or clamped to displace any excess monomer from themold cavity and to firmly seat the back curve mold part against aparting edge formed on the front curve mold part. The assembly isaccomplished under vacuum to speed the assembly of the mold and to avoidthe formation of gas bubbles from any gasses that might otherwise betrapped between the mold parts at the time of mold assembly.

It is also an object of the present invention to provide an apparatusand a method for precuring a polymerizable monomer or monomer mixture toform a soft contact lens in a mold which enables a more uniform cure forthe lens during the cure step, and which reduces “puddling” orcavitation of the lens from the mold during cure. The mold halves aretransported from the mold filling and mold assembly station to a precurestation, where they are clamped together under predetermined pressurefor a predetermined period of time in a low oxygen environment. Thesecond or convex mold half is thinner than the first or concave moldhalves to enable mold compliance during cure as the monomer or monomermixture is polymerized. The clamping pressure aligns flanges formed onthe first and second mold half to ensure that the flanges are paralleland that the respective curves of the molds are aligned. The clampingpressure also seats the back curve mold half against an annular edgeformed on the front mold half to essentially sever any excess monomerfrom the monomer contained within the mold cavity, thus ensuring thebest possible lens edge quality.

After a predetermined clamping period, the monomer or monomer mixture isexposed to actinic radiation, such as a UV light source, to partiallycure the monomer or monomer mixture to a gel state. After a secondpredetermined period of exposure under clamping pressure, the clampingaction and the UV radiation are removed, and the partially precured gellike lens is then transported in the mold through an extended curingstation for complete polymerization and cure.

It is also an object of the present invention to provide methods andapparatuses that can easily and repeatably separate the contact lensmold portions having a contact lens formed therebetween without damagingthe lens.

It is a further object of the present invention to provide a method andapparatus for separating a back curve mold from a front curve moldwherein a significant temperature gradient is created between the backcurve mold and the contact lens contained in a cavity formed between thetwo mold portions.

It is another object of the invention to create this temperaturegradient without excessive environmental heating or waste of energythrough the use of laser beams or high energy steam nozzles.

It is another object of the present invention to provide an automatedmeans to mechanically and reliably pry the mold halves apart in aconsistent and reliable manner to thereby enhance the production ofdefect free lenses, and minimize the tearing of the lens or the breakageof the lens mold parts.

It is another object of the present invention to provide a method ofcontrolling which mold half the lens sticks to by controlling thetemperature gradient and pressure applied to the assembled mold duringlens demolding.

Further benefits and advantages of the invention will become apparentfrom a consideration of the following detailed description given withreference to the accompanying drawings, which specify and show preferredembodiments of the invention.

Aspects and preferred features of the contact lens manufacturing systemin part described and claimed herein are detailed in copending andcommonly assigned application Ser. No. 08/257,802 of Martin et al. for“Low Oxygen Molding of Soft Contact Lenses”; application Ser. No.08/257,801 of Walker et al. for “Laser Demolding Apparatus and Method”;application Ser. No. 08/257,786 abandoned in favor of Ser. No.08/462,811, abandoned in favor of Ser. No. 08/729,711 now U.S. Pat. No.5,744,357 of Wang et al. for “Contact Lens Production Line PalletSystem”; application Ser. No. 08/257,267 of Lust et al. for “Apparatusfor Removing and Transporting Articles from Molds”; application Ser. No.08/257,785 of Lust et al. for “Mold Halves and Molding Assembly forMaking Contact Lenses”; application Ser. No. 08/258,264 of Martin et al.for “Method and Apparatus for Contact Lens Mold Filling and Assembly”;application Ser. No. 08/258,265 of Kindt-Larsen et al. for “MoldSeparation and Apparatus; application Ser. No. 08/257,792 of Martin etal. for “Mold Clamping and Precure of a Polymerizable Hydrogel”;application Ser. No. 08/258,263 of Kindt-Larsen et al. for “Method andApparatus for Applying a Surfactant to Mold Surfaces”; application Ser.No. 08/257,799 of Martin et al. for “Ultraviolet Cycling Oven forPolymerization of Contact Lenses”; application Ser. No. 08/258,557 ofMartin et al. for “Automated Apparatus and Method for Preparing ContactLenses for Inspection and Packaging”; and U.S. Pat. No. 5,294,379 ofRoss et al. for “Laser Assisted Demolding of Ophthalmic Lenses”, thedisclosures of which are incorporated herein by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing objects and advantages of the present invention for acontact lens production line pallet system may be more readilyunderstood by one skilled in the art with reference being had to thefollowing detailed description of several preferred embodiments thereof,taken in conjunction with the accompanying drawings wherein likeelements are designated by identical reference numerals throughout theseveral views, and in which:

FIG. 1 is a flow diagram of the continuous process for contact lensproduction, including molding, treatment and handling of the molds andcontact lenses in a low oxygen environment.

FIG. 2 is a top elevational planar view of the production line systemconstructed according to the present invention;

FIGS. 3 and 3(a) are respectively, a top or planar view and an elevationor side view of one embodiment of a first (female) or front curve moldhalf molded pursuant to the present invention;

FIG. 3(b) is an enlarged detail of a portion of FIG. 3(a).

FIGS. 4 and 4(a) are respectively a top or planar view and an elevationor side view of one embodiment of a second (male) or back curve moldhalf molded pursuant to the present invention;

FIG. 5 is an enlarged cross-sectional view of a pair of assembled moldhalves supported and registered in a pallet cavity.

FIG. 6 is a cross-sectional view of a typical production line conveyorand a clamp apparatus used to pause pallet movement.

FIG. 7(a) is a top plan view of a production line pallet carrier, usedto transport a plurality of contact lens molds throughout the contactlens production facility;

FIG. 7(b) is a side elevational view of the production line palletcarrier illustrated in FIG. 7(a);

FIG. 7(c) is a bottom plan view of the production line pallet carrierillustrated in FIG. 7(a).

FIG. 8(a) is a simplified plan view of the first section of an automatedline for the molding of contact lenses, and includes diagrammatic planviews of the injection apparatus and robotic material handling devicesused to prepare and transfer mold halves for the lenses to be molded;

FIG. 8(b) is a simplified plan view of a second section of the automatedline for molding contact lenses, which illustrates the filling andassembly stations and a precure station utilized in the practice of thepresent invention;

FIG. 8(c) is a simplified plan view of a third section of the automatedline for molding contact lenses, which illustrates the curing ovens forthe lenses;

FIG. 8(d) is a simplified plan view of a fourth section of the automatedline for molding contact lenses, which illustrates the demolding stationfor the lenses.

FIG. 9 is a simplified diagrammatic view of a monomer degassing andpumping system utilized in the present invention.

FIG. 10(a) is a diagrammatic illustration of a front curve mold halfbeing filled with monomer pursuant to the present invention;

FIG. 10(b) is a diagrammatic illustration of the application of a moldrelease surfactant to a portion of the front curve mold half;

FIG. 10(c) is a diagrammatic illustration of the transfer of the backcurve mold half pursuant to the method of the present invention;

FIG. 10(d) is a diagrammatic illustration of the mold assembly andclamping step used in the method of the present invention.

FIG. 10(e) is a diagrammatic flow chart of the method of filling andassembling the mold halves of the present invention.

FIG. 11 is a partially cross-sectioned side view of the filling moduleused for depositing a predetermined amount of monomer or monomer mixturein each of the mold cavities.

FIG. 12 is a partially cross-sectioned elevation view of a stampingstation for the application of a surfactant to a stamping head andthereafter for the deposition of a film of the surfactant onto a surfaceportion of the front mold half.

FIG. 13 is a diagrammatic time line illustration of the assembly step ofthe present invention.

FIG. 14(a) is a diagrammatic side view of the exterior of the assemblymodule of the present invention;

FIG. 14(b) is a partially cross-sectioned side view of the assemblymodule illustrated in FIG. 8(a).

FIG. 15 is a diagrammatic and partially cross-sectioned illustration ofthe dosing or filling station of the present invention illustrating thevacuum interconnections to the reciprocating filling module.

FIG. 16 is a diagrammatic and partially cross-sectioned illustration ofthe assembly station of the present invention illustrating the vacuumsupply lines for the reciprocating assembly station.

FIG. 17 is a partially cut away elevation view of one of the embodimentsfor precuring a polymerizable monomer or monomer mixture to form a softcontact lens.

FIG. 18(a) is a diagrammatic illustration of one embodiment of thepresent invention which uses an air driven clamp for clamping the moldhalves together;

FIG. 18(b) is a diagrammatic illustration of a second embodiment of thepresent invention which uses a spring driven clamp for clamping the moldhalves together.

FIG. 19 is a partially cross-sectioned elevation view of a reciprocatingportion of one embodiment of the present invention suitable forprecuring a polymerizable monomer or monomer mixture to form a contactlens.

FIG. 20 is an end elevational view of the apparatus illustrated in FIG.19.

FIG. 21 is an elevational end view of a second embodiment of the presentinvention used to precure a polymerizable monomer or monomer mixture toform a soft contact lens.

FIG. 22 is an elevational side view of the apparatus illustrated in FIG.21.

FIG. 23 is a partially cross-sectioned view of one of the polymerizationor curing units illustrated in FIG. 8(c).

FIG. 24 is a diagrammatic and isometric view of one embodiment of thedemolding apparatus used to demold the mold assembly in the laserdemolding embodiment of the present invention.

FIG. 25 is a schematic diagram of an optical train used in a laserembodiment of the invention.

FIG. 26(a) is a planar view of the front curve retaining means used inthe laser demolding embodiment of the present invention;

FIG. 26(b) is a partially cross-sectional view of a portion of the laserdemolding embodiment illustrating the front curve retaining guides.

FIGS. 27(a)-(c) are, respectively, a first elevation view, a top or planview and a side elevation view of the laser demolding apparatus of thepresent invention.

FIG. 28 is a partially cross-section elevation view of a walking beamtransport means that may be used to provide precise positioning of thepallet of FIG. 7.

FIG. 29 is a diagrammatic side view showing generally two sets of pryfingers that separate to lift a back curve lens mold from a front curvelens mold.

FIGS. 30(a)-(d) illustrate in detail the sequence of steps forseparating a back curve mold half from a front curve mold half of aplurality of contact lens molds in a second embodiment of the demoldingstation of the present invention; wherein

FIG. 30(a) illustrates the device with the steam nozzles engaging themold parts and the pry fingers engaging the mold flanges;

FIG. 30(b) illustrates the retraction of the steam nozzles, andengagement of the suction cup assembly;

FIG. 30(c) illustrates the upward pry motion of the assembly to removethe back curve mold part from the front curve mold and molded lens;

FIG. 30(d) illustrates the retraction of the pry fingers to allowremoval of the back curve mold parts by the suction assembly, andadvancement of the pallet containing the partially demolded lenses.

FIG. 31 is a partial plan view of the demolding assembly illustratingtwo sets of pry fingers for each of the pallets conveyed on a pair ofconveyors.

FIG. 32 is a detailed elevational view of a steam discharging apparatusthat may be used with the present invention.

FIG. 33 is a detailed cross-sectional view of the nozzle for dischargingsteam against the back curve lens mold surface.

FIG. 34 is a top plan view of the steam discharge manifold of theapparatus illustrated in FIG. 32 for distributing steam to each of thenozzle assemblies of the steam discharging apparatus.

FIG. 35 is a top plan view of the condensate manifold of the apparatusillustrated in FIG. 32 for venting excess steam pressure during steamimpingement to regulate the amount of steam discharged to the back curvelens mold surface.

FIG. 36 is a detailed cross-sectional view of the steam intake valve ofthe steam discharge apparatus illustrated in FIG. 32.

FIG. 37 illustrates in a top or plan view the suction cup assemblyuseful in the demolding station illustrated in FIG. 30.

FIG. 38 illustrates a side elevation view of the suction cup assemblyillustrated in FIG. 37.

FIG. 39 illustrates a front elevational view of the suction cup assemblyillustrated in FIG. 37.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In accordance with the present invention, lens mold blank preparation isintegrated with lens blank manufacture to minimize the time of exposureof lens blank molds to oxygen prior to implementation of the curingstage. Given that even a one minute delay between filling (introductionof the reactive monomer composition to the cavity of the concave lensmold section) and curing would require five hours of degas to achieve atarget minimum of 1×10⁻⁸ moles/cm³ concentration of oxygen at thereactivemonomer/mold interface, the facility of in line preparation ofthe lens mold blanks will be appreciated.

Reduction in oxygen levels is thus achieved not by degas alone, aspracticed in the prior method, but in the high temperative conditionsobtained in the molding equipment, and the fresh molding of a fullydegassed mold blank which is as soon as possible blanketed in an inertgas such as nitrogen for further handling through filling, precure andfinal cure.

It has been determined that a key parameter in controlling oxygen levelsat the mold interface is the diffusivity of oxygen into and from themold surface in response to ambient conditions, and thereafter to andinto the mold/reactive monomer composition. Molded lens molds readilyaccept via adsorption and absorption mechanisms an unacceptably highlevel of retained but migratable oxygen relative to the sensitivity ofthe reactive monomer composition, particularly in the case of thepreferred polystyrene mold component. For the purpose of thisapplication, both adsorption and absorption mechanisms are summarized bythe use of the term absorption. The migration of oxygen responds toconcentration such that when a mold is subjected to a vacuum, it willmigrate at applicable diffusion rates to the lesser concentration, inthis instance the vacuum. Naturally, the surface of the mold will be thelast portion to fully degas, leading to the unacceptably long degastimes for conditioning pretreatment. For similar reasons, readsorptionof oxygen will occur at the surface, and reequilibration to the interiorwill again be controlled by diffusion rates in the mold material, henceany exposure to the atmosphere will rapidly result in unacceptably highlevels of oxygen at the mold interface, which only relatively extensiveconditioning treatment will resolve, as a portion of the surfacesituated oxygen will diffuse to the oxygen poor interior, and then mustbe reacquired to the surface prior to elimination to the vacuum, orinert gas medium.

The recognition that diffusion of sorbed oxygen from the interior of thelens mold could lead to disruption of lens quality even where surfaceshad been swept of residual oxygen, thus lead to a further modificationof processes for the handling of lens mold for and through the moldingprocess. Specifically, every exposure of the lens mold to the atmospherecould be expected to lead to further sorption of oxygen which woulddiffuse in part to the interior of the part. In consequence, surfaceflushing with nitrogen alone, without diffusion time, would not besufficient to avoid molding problems derivative from the presence ofoxygen, as in an oxygen starved inert atmosphere, the oxygen stored inthe interior of the lens mold would readily and relatively rapidlydesorb to the surface. Then, once the mold was filled with reactivemonomer, no amount of flushing would resolve the problem.

It was then realized that for every atmospheric exposure, the lens moldwould optimally be wholly degassed, hence only by minimizing the time ofsuch exposures, and holding the lens mold under nitrogen for a time topermit essentially complete degassing could the problem be resolvedsatisfactorily. According to the invention, the injection moldingoperations previously performed off-site are physically integrated intothe contact lens manufacturing line. With the high temperature andpressure of the mold equipment, the initially high oxygen levels on thepelletized feed are efficiently cleared and the fresh surfaces formed inthe molding process are readily and preferentially purged of residualoxygen. The pelletized feed may also be degassed with nitrogen in thehopper of the injection mold.

While the preferred mold material is polystyrene, the molds can be madefrom any thermoplastic material which is suitable for mass productionwhich can be molded to an optical quality surface, which is transparentto the radiation used for polymerization and which has mechanicalproperties which will allow the mold to maintain its critical dimensionsunder the process conditions employed in the process discussed in detailbelow. Examples of suitable thermoplastic materials include polyolefinssuch as low, medium, and high density polyethylene, polypropylene,including copolymers thereof; poly-4-methylpentene; and polystyrene.Other suitable materials are polyacetal resins, polyacrylethers,polyarylether sulfones, nylon 6, nylon 66 and nylon 11. Thermoplasticpolyesters and various fluorinated materials such as the fluorinatedethylene propylene copolymers and ethylene fluoroethylene copolymers mayalso be utilized.

It has been found that with the need for a high quality, stable mold andespecially for the use of a plurality of molds in high volume operationsthe choice of material for the molds is significant. In the presentinvention the quality of production is not assured by individualinspecting and sorting each lens for power and curvature. Instead thequality is assured by keeping the dimensions of each individual moldmember within very tight tolerances and processing molds in particularsequential steps to give all lenses equal treatment. Since polyethyleneand polypropylene partly crystallize during cooling from the melt thereis a relatively large shrinkage giving dimensional changes difficult tocontrol. Thus, it further has been found that the most preferredmaterial for the molds used in the present process is polystyrene whichdoes not crystallize, has low shrinkage, and can be injection molded atrelatively low temperatures to surfaces of optical quality. It will beunderstood that other thermoplastics, including those mentioned above,may be used provided they have these same properties. Certain copolymersor blend of polyolefins that exhibit these desirable characteristics arealso suitable for the present purposes as are polystyrene copolymers andblends having such characteristics, as described more fully in U.S. Pat.No. 4,565,348.

For efficiency, ease of operation, and cycle times, injection moldingdevices are preferred. The cycle time for purposes of an automatedoperation is minimized, wherein average material throughput is as littleas 3 to 12 seconds and preferably 6 seconds is achieved under theinventive conditions described in U.S. application Ser. No. 08/257,785of Lust et al during which the material is heated to a thermoplasticcondition, extruded into the molds and ejected or removed from the mold.However, the maximum manifold temperature of 270-280° C. is achievedonly for a fraction of the material throughput time, and the moldtemperature is 215-220° C., hence it was surprising that the injectionmold operation was found capable of delivering essentially fullydegassed mold sections in each cycle.

Unlike prior practice as described in U.S. Pat. No. 4,565,348, the moldis designed to produce fully formed lens mold parts directly, that iswithout associated support structure such as a frame; there is inconsequence no need to dissociate the part from unneeded polymermaterial on demolding, and the lens mold parts may be directly collectedby automated robotic means for delivery to the transport means. In anygiven cycle, any number of mold parts may be prepared but forconvenience of handling, typically 8 lens mold parts of concave orconvex configuration are prepared in a given cycle and transferred byautomated robotic means to a pallet of aluminum or stainless steel inwhich they are received and supported in a regular spatial array adaptedfor further operations.

As illustrated in FIGS. 1 and 2 injection molds #1 and #2, shown atsteps 101 and 102 in the flow diagram of FIG. 1, mold respectively frontcurve and back curve lens mold parts or sections, in matched sets; theymay be located in tandem as shown in FIG. 2 or to shorten exposure tothe atmosphere still further, they may be located in a common planeintersecting a bifurcated transport line, even perpendicularly orientedthereto in the same plane.

Robotic means 103,104 are provided adjacent the mold registry andengagement station for receiving concave and convex lens moldsrespectively and transferring said mold part to a low oxygen environmentat a high production cycle rate, as noted at step 105.

In the course of or following complete degassing of the lens moldsections as indicated at 106 in FIG. 1, the pallets containing concaveand convex lens mold sections are ordered into interleaved relation anddegassed on enclosed infeed conveyor such that automated equipment mayeffect their operative interengagement into molding relation.

The sequencing conveyor 32 including the interleaving station 40 isenclosed and pressurized over its entire length with an inert gas,conveniently nitrogen. The amount of nitrogen is not critical, it beingsuitable to use just enough nitrogen pressure to effectively exclude theatmosphere under the operating conditions experienced. In the nitrogentunnel surrounding sequencing conveyor 32 the freshly prepared lens moldblanks are degassed as indicated at step 106 in FIG. 1.

The concave lens molds are filled with the reactive monomer compositionat step 107 and the concave and convex lens molds are placed intoregistry and urged 10 into complementary molding relation. The fillingand assembly zone 50 surrounds a portion of the conveying or transportmeans 32, which delivers to the zone pallets of concave and convex lensmold sections, respectively, and at the terminus of the zone carriespallets of paired and filled molds to the precure zone. The filling andassembly zone illustrated in FIG. 2 at 50 is defined by a geometricallyappropriate, transparent enclosure, generally of rectangularcross-section, formed of any suitable thermoplastic or metal andthermoplastic construction.

As illustrated at 107 in FIG. 1, the concave lens mold sections arefilled with degassed monomer composition from step 108, and thentransported to an assembly module having a vacuum chamber formedintermittently within the nitrogen tunnel in which filled concave lensmolds are engaged with convex mold sections in vertical alignment and inmating relation, such that the reactive monomer composition is trappedbetween the optical surfaces of the respective mold sections and atleast partially sealed by the engagement, of the parting edge formedperipherally in each of the lens mold sections. The vacuum is releasedand the mated mold is passed through nitrogen to the precure station, anintegral part of the nitrogen tunnel.

As will hereinafter be explained in detail, the vacuum chamber is formedupon and about a single pallet by the periodic reciprocable motion ofapparatus also comprising means for alignment of the seating of theconvex mold sections upon the concave mold sections so their axes ofrotation are collinear and their respective flanges are parallel. Uponsealing engagement with the pallet the thus formed chamber is evacuatedin order to ensure that no gas bubbles are entrapped between and uponthe respective optical molding surfaces. The degree of vacuum isselected for the purpose of speeding the assembly of mold parts andremoving any gas bubbles at the monomer/mold interface that mightotherwise be entrapped in the course of closure between thecomplementary mold sections.

Following assembly of the mold parts, the incipient lens monomer isprecured at step 109 in the precure module 60 of the present invention.The process of the precure involves clamping the mold halves inregistration and then precuring the monomer or monomer mixture to a gellike state.

Following precure, the polymerization of the monomer or monomer mixtureis completed in curing tunnel 75 as indicated at step 110 as will behereinafter explained in detail.

Following complete polymerization, the lenses are demolded by heatingthe back curve mold and then prying from the front curve and mold in thedemold assembly 90 as indicated at step 111. Finally, the lens ishydrated, inspected and packaged as indicated at step 112.

Thus, the invention permits the generation of high optical quality softcontact lenses in volume and at high speed, with a low defect count.

Referring to FIGS. 1 and 2, the first and second injection molds 101(a)and 102(a) are continuously cycled to periodically produce (generally,from 3 to 12 seconds, and preferably, about 6 seconds) sets of concaveand convex lens mold parts or sections which are collected from molds atthe end of each cycle. In the geometric configuration obtaining, (andpreferred for better manipulative exchange) the mold upon opening fordemolding present the finished lens mold parts in or close to thevertical plane, generally −5 to 10° from the vertical. As illustrated inFIG. 2 and noted at step 105 in FIG. 1, a plurality of fingers of thearticulated robotic means 103, 104 gently engage and receive the set ofmolds and while maintaining same in essentially the same spatialrelation, rotates them from a plane generally perpendicular to thetransport line through 90° to a parallel plane above the transport meanswhile simultaneously or sequentially rotating toward and engaging thehorizontal plane of the transport line, and releases the mold parts intoregistry with carrier pallets on conveyor means indicated generally at27,29 in FIG. 2.

The robotic transporting assemblies generally depicted at 103,104 inFIG. 2, deposit the back curve mold parts directly on a production linepallet that has been momentarily paused by a clamping means.

As will be hereinafter explained with reference to FIG. 8(a), the frontcurve mold parts or halves are removed form the injection mold 10(a) inan inverted orientation to avoid any possible contact with the opticalsurface of the mold half. The front curve halves are then inverted byanother robotic transfer device and deposited on a stationary pallettherebelow.

After receiving the sets of mold parts, the pallets are advanced by thebelt conveyors 27,29, in the direction indicated by the arrows in FIG. 2into a low oxygen environment, generally indicated by housing means 24.Housing means 24 is pressurized with N₂ as indicated, and may optionallybe equipped with air lock means at each entry and egress point of thelow oxygen environment.

FIGS. 3 and 3(a) illustrate respectively top elevational and side viewsof one embodiment of a first or front mold half 10 useful in theproduction of a contact lens by the polymerization of a monomer ormonomer mixture in a mold assembly composed of two complementary frontand base mold halves. The front mold half 10 is preferably formed ofpolystyrene but could be any suitable thermoplastic polymer such asmentioned hereinabove which is sufficiently transparent to ultravioletor visible light to allow irradiation therethrough with light to promotethe subsequent polymerization of a soft contact lens. Alternatively,other forms of radiant energy could be used providing the front moldhalf is transparent to that form of energy. A suitable thermoplasticsuch as polystyrene also has other desirable qualities such as beingmoldable to surfaces of optical quality at relatively low temperatures,having excellent flow characteristics and remaining amorphous duringmolding, not crystallizing, and having minimal shrinkage during cooling.

The front mold half 10 defines a central curved section with an opticalquality concave surface 15, which has a circular circumferential partingedge 14 extending therearound. The parting edge 14, shown in enlargeddetail in FIG. 3(b), is desirable to form a sharp and uniform plasticradius parting line (edge) for the subsequently molded soft contactlens. A generally parallel convex surface 16 is spaced from the concavesurface 15, and an annular essentially uniplanar flange 18 is formedextending radially outwardly from the surfaces 15 and 16 in a planenormal (perpendicular) to the axis (of rotation) of the concave surface15. The concave surface 15 has the dimensions of the front curve (powercurve) of a contact lens to be produced by the front mold half, and issufficiently smooth such that the surface of a contact lens formed bypolymerization of a polymerizable composition in contact with thesurface is of optically acceptable quality. The front mold half isdesigned with a thinness (typically 0.8 mm) and rigidity effective totransmit heat therethrough rapidly and to withstand prying forcesapplied to separate the mold half from the mold assembly duringdemolding.

The front mold half or curve thickness was reduced from 1.5 mm in priordesigns to 0.8 mm. This has a direct impact on cycle time reduction.

FIGS. 4 and 4(a) illustrate respectively top elevational and side viewsof one embodiment of a second, or back curve mold half 30. The backcurve mold half is designed with all of the same design considerationsmentioned hereinabove with respect to the front curve mold half 10.

The back curve mold half 30 is also preferably formed of polystyrene butcould be any suitable thermoplastic such as those mentioned hereinabovewhich is transparent to visible or ultraviolet light. The back curvemold half 30 defines a central curved section with an optical qualityconvex surface 33, a generally parallel concave surface 34 spaced fromthe convex surface 33, and an annular essentially uniplanar flange 36formed extending radially outwardly from the surfaces 33 and 34 in aplane normal to the axis (of rotation) of concave surface 34. The convexsurface 33 has the dimensions of the rear curve (which rests upon thecornea of the eye) of a contact lens to be produced by the base moldhalf, and is sufficiently smooth such that the surface of a contact lensformed by polymerization of a polymerizable composition in contact withthe surface is of optically acceptable quality. The base mold half isdesigned with a thinness (typically 0.6 mm) to transmit heattherethrough rapidly and rigidity effective to withstand prying forcesapplied to separate the mold half from the mold assembly duringdemolding.

The base curve is designed with a base curve sag of 5.6 mm (see FIG.4(a) for the predetermined sag, dimension “Y”). The base curve sag andthickness of 0.5 mm serves two purposes:

1. The base curve sag results in a gap of 1.5 mm-3.0 mm between theassembled base curve and front curve, which assists in mechanicallyremoving the base curve from the front curve matrix after polymerizationwhich forms a contact lens.

2. With a part thickness on the order of 0.6 mm, the base curve reducesthe occurrence of weld lines on the distal side of the flange (where twomelt flows converge) which could detrimentally cause a fracture line onthe base curve.

The mold halves 10,30 define generally triangular tabs 26,37 integralwith the flange which project from one side of the flange. The tab 37extends to the injection hot tip which supplies molten thermoplastic tothe mold, and also defines therein an angled (e.g., 45°) web sections22,38 for smoothing the flow of the polymer wave front and thus to avoidjetting, sink marks, weld lines and other undesirable flows which wouldimpair the optical quality of the mold half. The mold halves 10,30 alsodefine a small circular projections 25,35 which serve as traps in themolding process to immobilize small plugs of colder polymers that mayform at the injection hot tip between cycles.

The monomer and monomer mixtures to which this process may be directedinclude copolymers based on 2-hydroxyethylmethacrylate (“HEMA”) and oneor more comonomers such as 2-hydroxyethyl acrylate, methyl acrylate,methyl methacrylate, vinyl pyrrolidone, N-vinyl acrylamide,hydroxypropyl methacrylate, isobutyl methacrylate, styrene, ethoxyethylmethacrylate, methoxy triethyleneglycol methacrylate, glycidylmethacrylate, diacetone acrylamide, vinyl acetate, acrylamide,hydroxytrimethylene acrylate, methoxyethyl methacrylate, acrylic acid,methacryl acid, glyceryl methacrylate, and dimethylamino ethyl acrylate.

Preferred polymerizable compositions are disclosed in U.S. Pat. No.4,495,313 to Larsen, U.S. Pat. No. 5,039,459 to Larsen et al. and U.S.Pat. No. 4,680,336 to Larsen et al., which include anhydrous mixtures ofa polymerizable hydrophilic hydroxy ester of acrylic acid or methacrylicacid and a polyhydric alcohol, and a water displaceable ester of boricacid and a polyhydroxyl compound having preferably at least 3 hydroxylgroups. Polymerization of such compositions, followed by displacement ofthe boric acid ester with water, yields a hydrophilic contact lens. Themold assembly of the present invention described herein may be used tomake hydrophobic or rigid contact lenses, but the manufacture ofhydrophilic lenses is preferred.

The polymerizable compositions preferably contain a small amount of across-linking agent, usually from 0.05 to 2% and most frequently from0.05 to 1.0%, of a diester or triester. Examples of representative crosslinking agents include: ethylene glycol diacrylate, ethylene glycoldimethacrylate, 1,2-butylene dimethacrylate, 1,3-butylenedimethacrylate, 1,4-butylene dimethacrylate, propylene glycoldiacrylate, propylene glycol dimethacrylate, diethylglycoldimethacrylate, dipropylene glycol dimethacrylate, diethylene glycoldiacrylate, dipropylene glycol diacrylate, glycerine trimethacrylate,trimethylol propane triacrylate, trimethylol propane trimethacrylate,and the like. Typical cross-linking agents usually, but not necessarily,have at least two ethylenically unsaturated double bonds.

The polymerizable compositions generally also include a catalyst,usually from about 0.05 to 1% of a free radical catalyst. Typicalexamples of such catalysts include lauroyl peroxide, benzoyl peroxide,isopropyl percarbonate, azobisisobutyronitrile and known redox systemssuch as the ammonium persulfate-sodium metabisulfite combination and thelike. Irradiation by visible light, ultraviolet light, electron beam ora radioactive source may also be employed to catalyze the polymerizationreaction, optionally with the addition of a polymerization initiator.Representative initiators include camphorquinone,ethyl-4-(N,N-dimethylamino)benzoate, and4-(2-hydroxyethoxy)phenyl-2-hydroxyl-2-propyl ketone.

Polymerization of the monomer or monomer mixture in the mold assembly ispreferably carried out by exposing the composition to polymerizationinitiating conditions. The preferred technique is to include in thecomposition, initiators which work upon exposure to ultravioletradiation; and exposing the composition to ultraviolet radiation of anintensity and duration effective to initiate polymerization and to allowit to proceed. For this reason, the mold halves are preferablytransparent to ultraviolet radiation. After the precure step, themonomer is again exposed to ultraviolet radiation in a cure step inwhich the polymerization is permitted to proceed to completion. Therequired duration of the remainder of the reaction can readily beascertained experimentally for any polymerizable composition.

As indicated at step 108 in FIG. 1, the monomer or monomer mixture isdegassed prior to the filling of the front curve mold half in order toremove dissolved gases. O₂ is removed because of its deleterious effecton polymerization as noted above. Other gases, including N₂, are removedto avoid the formation of gas bubbles when the monomer is expelled fromthe relatively high pressure of the pump line which supplies the fillnozzle, to encounter the atmospheric or subatmospheric N₂ pressure ofthe filling and assembly chambers.

As illustrated in FIG. 9 the polymerizable monomer or monomer mixture isprovided in containers 400, typically 15 liters in volume. The containeris connected to the monomer degassing system by means of line 412.Suction is developed by pump 414 to draw the monomer from the drum 400,through line 412, to pump 414, and out the pump discharge 416. Whilegoing through discharge line 416, the monomer passes through filter 418in order to remove any extraneous particulate contaminants that may bepresent in the monomer.

The monomer is then provided to the inlet 420 of the degas unit 422.Within the degas unit, the monomer is divided among a plurality of tubes424, and then recombined into a degas unit discharge 426. The degas unitis operated under a low ambient pressure, typically around 4 torr whichis provided by vacuum pump 428. This vacuum pump is attached to thedegas unit 422 by line 430 and discharges the excess air from the degasunit by way of line 432. The tubing members 424 are formed preferably ofa gas permeable tubing such as STHT tubing produced by Sanitec, Inc. ofAndover., N.J. from Q74780 Medical Grade Silicon Rubber manufactured byDow Corning of Midland, Mich. While two tubes are illustrated in FIG. 9,it is understood that a plurality of tubes, typically 10 tubes areprovided for the degas unit 422.

After the monomer exit the degas unit 422 by discharge line 426, itpasses through an oxygen monitor 434. This monitor measures the residualoxygen within the monomer to insure that the degas unit is functioningproperly. If the oxygen content of the monomer is indicated as being tohigh, operation of the production line can be halted until the problemis corrected in order to avoid the production of defective lenses.

Once oxygen monitor 434 has determined that the oxygen content of themonomer is sufficiently low, the monomer passes through line 436 intomanifold 438. The manifold is used as a common source to supply aplurality of precision dose pumps 440 used to fill the individualcontact lens mold at the monomer filling and assembly dosing station 50.The pumps 440 used to pump the processed monomer delivered to manifold438 are pumps made by the IVEK Corporation, North Springfield, Vt. Thesepumps provide precision doses of degassed monomer to the mold cavities15 via nozzles 242. A return line 442 keep the monomer of the frontcurves 10 circulating when not pumped by pumps 440.

A top view of a production line pallet 12 for carrying production lensmold halves is shown illustrated in FIG. 7(a), with a side viewillustrated in FIG. 7(b) and a bottom view illustrated in FIG. 7(c). Itshould be understood that all pallets 12 are interchangeable in thatthey may accommodate either front curve or back curve contact lens moldhalves. In the preferred embodiment shown in FIG. 7(a), the productionline pallet 12 is formed of aluminum and may be 60 mm in width and 120mm in length. In another embodiment, the pallet 12 may be formed ofstainless steel and may be 80 mm in width and 160 mm in length.

Each pallet 12 contains a plurality of recesses for receiving arespective contact lens mold assembly 39 comprising a complimentaryfront 10 and back 30 curve mold halves which define the shape of thefinal desired lens. One such mold assembly 39 is shown seated within arecess 130(b) of the pallet in FIG. 5. The contact lenses are formed byplacing an amount of polymerizable monomer or monomer mixture, generallyon the order of about 60 μl, in each front curve (concave) mold half 10seated within a pallet recess 130(b) at the filling and mold assemblyapparatus 50. The desired amount depends on the dimensions (i.e., thediameter and thickness) of the desired lens, taking into account thegeneration of by-products upon polymerization and the exchange of waterfor those by-products and diluent, if any, following polymerization.Then, the back curve (convex) mold half is placed onto the polymerizablecomposition 11 with the first and second mold halves aligned so thattheir axes of rotation are collinear and the respective flanges 18,36are parallel. The mold halves are transported in an annular recess130(a) which receives and supports the annular flange 18 of the frontcurve mold half. In addition to the recesses 130(a) and (b), the pallets12 also have a plurality of oriented recesses 130(c) which receive thetriangular tab portions 26 of the seated front curve mold half 10 toprovide a predefined angular position thereof. The recesses 130(a) aredesigned to prevent movement of the normally seated mold half withineach recess up to within +/−0.1 mm. The triangular tab 37 of the secondor back curve mold half 30 overlies front curve tab 26 to enable acollinear axis of rotation with respect to the two mold halves, ifdesired.

As illustrated, in FIGS. 7(a)-7(c), pallet 12 of the present inventionis designed to ensure that a tight vacuum seal may be created with thesurface of the pallet during the monomer deposition and contact lensmold assembly phases of the production line facility. As will beexplained in further detail below, blind locating bushings 129(a) and129(b) are located at opposite ends of the pallet 12 to enable precisepositioning of the pallet within the various assemblies of theproduction line. These locating bushings enable a precise registrationof the pallet throughout the various assemblies of the contact lensproduction facility, and, thereby assist in the alignment of a tightvacuum seal to be created at the peripheral upper surface 140 of thepallet prior to assembling the mold halves. As shown in FIG. 7(a),proximate the center of each pallet 12(a) is a unique bar codeidentifier 135 for handling, tracking, and quality control purposes.

As further shown in FIGS. 7(b) and 7(c), the outer peripheral edges ofthe pallet 12 define a notch or indentation 28(a),(b) for engaging acomplementary guide rail or shoulder for enabling precise registrationof the pallet at the demolding apparatus, as will be explained ingreater detail below. Additionally, the pallet 12 includes blind holes128(a) and 128(b) wherein an optic bore scope or similar viewing devicemay be inserted to enable real time viewing of the contact lensproduction process at the surface of the pallet.

FIG. 8(a) illustrates in detail the robotic transporting assemblies103,104 of FIG. 2 for rapidly transporting respective front curve andback curve mold portions from respective injection molds 101(a) and102(a) to respective pallets 12(a) and 12(b). A detailed description ofthe mold cavities of injection mold assemblies 101(a) and 102(a) may befound in the aforementioned co-pending U.S. patent application Ser. No.08/257,794 “Mold Insert Design to Achieve Short Mold Cycle Time”assigned to the same assignee as the instant invention. A detaileddescription of each transporting assembly 103 and 104 may be found inco-pending U.S. patent application Ser. No. 08/257,267 entitled“Apparatus for Removing and Transporting Articles from Molds” assignedto the same assignee as the instant invention.

Generally, robotic transporting assembly 103 is provided with a firstrobotic assembly 715 for removing front curve lens molds from injectionmold assembly 101(a), and transporting the mold to a first location;assembly 717 is provided for receiving the front curve lens molds fromassembly 715 and transporting the molds from the first location to asecond location, and robotic assembly 716 is provided for receiving thefront curve lens molds from assembly 717 and transporting those moldsfrom the second location to an inverting hand 738(a) of invertingassembly 738 that inverts the orientation of the front curve moldscarried by the robot 716. This inversion is necessary because therobotic assembly 716 is handling the front curve molds by theirnon-optical (convex) side and the front curve molds must therefore beinverted to enable the non-optical surface of each mold to be placed inthe pallet 12(a) (under inverting hand 738(a)) that has been momentarilypaused to receive the front curve lens molds.

The robotic transfer assemblies 103,104 are more fully described withrespect to FIG. 8(a) as follows. Support subassemblies 716(a),(b) ofrobotic assembly 715(a),(b) are connected to hands 714(a),(b) to supportthe hands and to move the hands between molds 101(a),102(a) and thefirst location, which preferably is directly above transfer platforms717(a),(b) of the second robotic assembly 717,728. Preferably, supportframes 724(a),(b) are located adjacent molds 101(a),102(a) and supportsubassemblies 716(a),(b) are supported on frame 724(a),(b) for slidingmovement toward and away from molds 101(a),102(a). As the assemblies15(a),(b) slide along frames 724(a),(b), hands 714(a),(b) move with theassemblies toward and away from molds 101(a),102(a).

More specifically, arms 716(a),(b) are slidably mounted on frames724(a),(b), to extend outward from these frames, and are pivotallymounted on assemblies 715(a),(b) while hands 714(a),(b) are rigidlyconnected to the outward ends of arms 716(a),(b) for movement therewith.With this arrangement, arms 716(a),(b) carry hands 714(a),(b) toward andaway from molds 101(a),102(a), while allowing the hands to pivot betweena substantially vertical orientation, as shown in FIG. 8(a), and asubstantially horizontal orientation, to deposit the mold parts oncarriers 717(a),(b).

Preferably, arms 716(a),(b) are high speed, low mass assemblies, and areable to move hands 714(a),(b) into molds 101(a),102(a), and removearticles therefrom, at a rate of once every 3 to 12 seconds andpreferably every 6 seconds. Also, preferably the arm is constructed froma high strength, low mass material such as material sold under thetrademark Kevlar.

Each of the hands 714(a),(b) are equipped with a plurality of hollowcylindrical bellows, two of which are illustrated on each hand at720(a),(b). The bellows are connected to a vacuum manifold and vacuumline for engaging and securing the mold parts thereto as they areejected.

As previously mentioned, second robotic assemblies 717,728 receivearticles from first robotic assemblies 715(a),(b), at the firstlocation, and transport those articles to the second location; and,generally, second robotic assemblies 717,728 include support frames740(a),(b), platforms 717(a),(b), and tread covered support lines756(a),(b). Support frames 740(a),(b) have the general shape of anelongated cube or box and extend from a position located directly belowthe above-mentioned first location to a position directly below theabove-mentioned second location. The top portion of frames 740(a),(b)form channels 746(a),(b) that longitudinally extend between thetransverse ends of the support frame.

Transfer platforms 717(a),(b) are provided to receive articles fromfirst assembly 715(a),715(b), specifically hands 714(a),(b) thereof, andto carry those articles on support frames 740(a),(b) for sliding orrolling movement therealong.

The upper section of transfer platforms 717(a),(b) include or form amultitude of receptacles 766 for receiving and holding mold halvesreceived from hand members 714(a),(b). Preferably, receptacles 766 ontransfer platforms 717(a),(b) are located so that when hands 714 ofassemblies 15(a),15(b) are positioned directly above transfer platforms742(a),(b), each of the bellows 720 of hands 714(a),(b) are aligned witha respective one of the receptacles 726 of platforms 717(a),(b).

A moving means is provided to move the transfer platforms 717(a),(b)along frames 740(a),(b), and preferably the moving means includes a ballscrew and motor mounted within support frames 740(a),(b) and coupled tothe platforms 717(a),(b) by brackets. Treads 756(a),(b) protect androute the electrical vacuum and pneumatic support for the transferplatforms 717(a),(b). The tread protectors 756(a),(b) are locatedadjacent support frames 740(a),(b) and are supported for movementbetween extended and retracted positions.

A pair of third robotic assemblies 716,726 are illustrated and areprovided to receive articles from second assemblies 717,728, toreleasably hold those articles and to carry the articles to a thirdlocation. Support column 766(a),(b) supports robotic assemblies 716,726for movement between the second and third locations. More specifically,support columns 766(a),(b) are supported and extends upward between theabove-mentioned second and third locations. First arms 770(a),(b) ofrobotic assemblies 716,726 are supported by support columns 766(a),(b)for pivotal movement, and this first arm extends outward from thesupport column; and second arms 772(a),(b) are supported by first arms770(a),(b) for pivotal movement on one end of arms 772(a),(b) and extendoutward therefrom.

Preferably, a third vertical arm is provided for each robotic assemblythat is extensible, and this arm is extended and retracted to lower andraise hands 776(a),(b) indicated by dotted lines in FIG. 8(a). Anysuitable means may be used to extend and to retract the third arm; and,for instance, a hydraulic cylinder or screw motor may be mounted in therobotic assembly, with hands 776(a),(b) connected to a lower end of thehydraulic cylinder or screw motor.

Hands 776(a),(b) are provided for receiving and releasably holding themold halves, and preferably these hands also include a plurality ofbellows for gripping the mold halves.

In the operation of the robotic assemblies 716,726, arms 770(a),(b) arepivoted about column 766(a),(b) and arms 772(a),(b) are pivoted on arms770(a),(b) to the position shown in FIG. 8(a), where the arms and hands776(a),(b) are directly above the second extended position of transferplatforms 717(a),(b). Hands 776(a),(b) are then lowered toward or intoengagement with transfer platforms 717(a),(b) and the mold halves aretransferred from transfer platforms 717(a),(b) to hands 776(a),(b) andthe hands are then raised, clearing the hands from the transferplatforms 717(a),(b). Arms 770(a),(b) are then pivoted about columns766(a),(b), clockwise as viewed in FIG. 8(a), and, simultaneously, arms772(a),(b) are pivoted on arms 770(a),(b), counterclockwise as viewed inFIG. 8(a), until hands 716(a),(b) are located directly above theposition at which the mold halves are to be deposited. The vertical armsmounted on the second arms 772(a),(b) are then extended to lower hands776(a),(b), and the mold halves may be transferred from hand 776(a) topallet 738(a) of inverter 738 or from hand 776(b) directly on a pallet12(b) carried on conveyor 29.

To elaborate, when robotic transport assembly 103 carries mold halves,preferably all physical contact between the elements of robotic assembly103 and the mold half is on the sides of the mold that are opposite theoptical surfaces of those mold sections. In this way, there is nophysical contact between any part of robotic assembly 103 and thesurfaces of the mold that directly engage the hydrophilic material usedto form the contact lens molded between the mold halves. Thus, whenassembly 103 carries mold half away from injection mold 101(a), the moldhalf is inverted; while when assembly 104 carries a mold half away frominjection mold 102(a), the mold is in its position and ready for depositon a carrier pallet. Thus, when robotic assembly 103 carries mold halvesaway from injection mold 101(a), the mold half is not in the properorientation for transfer to pallet 12(a), and the mold half must beinverted in order to orient it properly for transfer to pallet 12(a).The preferred embodiment of inverter assembly 738 is provided to dothis.

As mentioned above, inverter assembly 738 includes hand 738(a) andsupport subassembly 786. Preferably, hand 738(a) includes a base andbellows to receive mold halves from the third robotic assembly 716,specifically hands 776(a) thereof, and to hold those articles while theyare inverted for transfer to pallet 12(a).

Support subassembly 786 is provided to move hand 738(a) of assembly 738between third and fourth locations, and in the preferred embodiment,support subassembly 786 is used to pivot and to reciprocate hand 738(a).With the embodiment of subassembly 738 illustrated in the drawings, arm794 extends outward from subassembly 786, and hand 738(a) is rigidlyconnected to an outward or second end of arm 794 for pivotal movementtherewith. Preferably, hand 738(a) is pivoted substantially 1800, from aposition in which the bellows on the hand extend directly upward to aposition in which these bellows extend directly downward. After receiptof the mold halves from hand 776(a), the inverter assembly 738reciprocates hand 738(a) downwardly and then releases the mold halvesonto a pallet 12(a) that has been temporarily paused by clamping means19(a),19(b) as will hereinafter be explained.

Each of the pallets is momentarily paused on conveyor belts 27,29 at thetime of transfer of the molds. In the preferred embodiment shown in FIG.8(a), and in elevation in FIG. 6, a clamping mechanism 19 comprising apair of clamping jaws 19(a),(b) are located at opposite sides of theconveyor 27 to timely clamp an empty pallet 12(a) and halt the motion sothat the front curve mold halves may be positioned on the pallet byinverting head 738(a), while a pair of clamping jaws 20(a),(b) arelocated to timely clamp an empty pallet 12(b) to halt its motion onconveyor 29 while the back curve mold halves are positioned on thepallet by robot assembly 726.

The front and back curve mold halves are also transferred from theirrespective injection mold assemblies 101(a),102(a) to a low oxygen, andpreferably, a nitrogen environment maintained around portions of thefront curve conveyor 27, back curve conveyor 29, and a sequencingconveyor 32 by housing 24. This inert environment is accomplished byenclosing each conveyor in an atmosphere of pressurized nitrogen gas. Aswill be explained below, the handling of the pallets and the contactlens mold assemblies throughout the various stations of the productionline facility are conducted in an inert, and preferably a nitrogen gasto provide a low oxygen environment for all of the component pars priorto polymerization. While it is possible to enclose injection moldassemblies 101(a),102(a) and robotic transport assemblies 103,104 withina nitrogen enclosure, it has been found that the use of the high speedrobotic assemblies illustrated in FIG. 8(a), a transfer can beaccomplished in under 15 seconds, with a mold cycle time of 6 seconds.The 15 second exposure to atmospheric oxygen requires only a 3 minuteresidence time under N₂ to degas O₂ adsorbed during the 15 seconds. A 3minute buffer on sequencing conveyor 32 also ensures an adequate supplyof molds for the assembly line. Opening the injection mold devices101(a),102(a) to atmospheric cooling alleviates substantial coolingproblems that would otherwise be encountered by running the moldingmachines in an enclosed environment.

The operation of the clamping mechanisms 19 and 20 will now be describedin view of FIG. 6. It should be mentioned that the operation of allclamping mechanisms hereinafter disclosed, is essentially the same asthe following description of the preferred embodiment. Specifically, theclamping mechanism 19 consists of one or more pneumatic cylinders 21that operates to push lower ends 44(a),(b) of clamping jaws 19(a),(b) sothe jaws pivot about associated clamping shafts 42(a),(b) to close inand enable respective fixed clamping blocks 19(c),(d) to grip pallet12(a) (shown in phantom lines in FIG. 6) that is positioned in alignmentwith the jaws 19(a),(b). As illustrated in the FIG. 6, the clampingblocks 19(c),(d) of clamping jaws 19(a),(b) are located just above andat opposite sides of the conveyor 27 while the pneumatic cylinder 21 ismounted below the conveyor 27.

To transport the pallets, each supply conveyor 27,29 comprises a drivemeans in the form of a motor driven belts, one of which is illustratedin cross-section in FIG. 6(a) as 43(a), which are strong enough tosupport pallets 12(a),(b) supplied to the sequencing apparatus 40. Asillustrated in FIGS. 7(b) and (c), a raised underside section 138 ofeach pallet 12(a),(b) may be coated with Nedox® or Tufram® so to enablesliding of the pallet when being held above a moving belt by clampingjaws 19,20 or pushed along slide plates at certain processing locationsof the plant.

The pallet conveyors 27,29 and 32 include a drive means for each of themotor driven belts. The motor drive means to conveyor 32 enables thetransport of thirty or more paired sets of pallets 12(a),12(b) carryingrespective front and back curve lens mold portions to be smoothly anduniformly transported at a preferred rate of approximately 30 mm/secuntil they are assembled for processing at the filling/mold assemblyapparatus 50. In a similar fashion, suitable motors drive respectiveconveyor belts 43(a),43(b) carrying the respective pallets 12(a),12(b)so that they are smoothly and uniformly transported at a preferred rateof approximately 75 mm/sec until their motion is terminated at the endsof each conveyor for sequencing as will be explained in further detailbelow. Additionally, idler rollers and tensioner roller may be providedfor adjusting the tension of the belts of conveyors 27,29 and 32.

FIG. 6 illustrates a cross-sectional, front view of a conveyor assembly27 shown carrying a pallet 12(a) on conveyor belt 43(a). It isunderstood that the view of FIG. 6 may apply to any of the otherabove-described conveyors 29 and 32 carrying pallets.

FIG. 8(a) illustrates the sequencing apparatus 40 (demarked by dottedlines in FIG. 8(a)) of pallet system comprising a double cross pusherwhich positions a pallet 12(a) from conveyor 27 (containing front curvecontact lens mold portions) next to a pallet 12(b) from supply conveyor29 (containing back curve contact lens mold portions) for conveyancealong the sequencing conveyor 32. The sequencing apparatus 40 is locatedat the ends of each supply conveyor 27, 29 and comprises a first arm 141and second arm 142 for simultaneously pushing pallets from respectivesupply conveyors 27 and 29 along track 143 for entry into the mainsequencing conveyor 32. As illustrated in FIG. 8(a), the first arm 141and second arm 142 are mounted in parallel on mounting means 145 that isslidable along track 147 in both directions as indicated by the doublearrow in FIG. 8(a). A lifting means, which may be pneumaticallyoperated, is provided for raising and lowering the first and second arms141,142 in a vertical direction above the plane of a horizontallypositioned pallet, as will be explained in further detail below. Whilethe arms 141,142 are in a raised position, the mounting means 145remains slidable along track 147 so that the first and second arms maybe retracted while in their raised position and subsequently loweredafter reaching their original positions.

In a first step of the sequencing process, the forward motion of apallet 12(a) from conveyor 27 is terminated at a first position “A”,just forward of the first arm 141, as shown in FIG. 8(a). Forward motionof the pallet 12(a) is terminated by a pair of upstream clamping jaws146(a),(b), that, in a timed fashion, open and close to let one palletalign with the first pusher arm 141 of the double pusher. When jaws146(a),(b) are closed, forward motion of the pallet is terminated and aplurality of pallets will accumulate behind the clamped pallet. At theappropriate time, one pallet may be released by opening the clampingjaws 146(a),(b) so that the forward motion of the accumulating palletson conveyor 27 will push the first lead pallet to a second positionindicated as “B” in FIG. 8(a), also in alignment with the first pusherarm 141. The jaws 146(a),(b) may be immediately closed to clamp the nextof the accumulated pallets to prevent their forward motion. The openingand closing of the clamping jaws 146(a),(b) may be appropriately timedto enable pallets to be sequentially input to the pusher in an orderlyfashion.

After appropriate sensing, and, as controlled by a computer or aprogrammable logic controller, the arms 141,142 of double cross pusher40 are caused to slide along track 147 in the first direction from S toS′ indicated by the double headed arrow S-S′ in FIG. 8(a) so that firstarm 141 pushes pallet 12(a) to a second position that is located justforward of second arm 142 position and indicated by arrow “C” in FIG.8(a). It is understood that during initialization of the sequencer, thesecond arm 142 did not push a pallet since none were positioned formovement in front of second arm. The lifting means is then commanded toraise the first and second arms 141,142 so that the mounting means andthe arms may be retracted along track 147 and subsequently lowered backat their original position as shown in FIG. 8(a).

The following description demarcates where steady state sequencingoperations begin. As shown in FIG. 8(a), after retracting first andsecond arms 141,142 to their original position, or, preferably, whilethe arms are in their raised position while being retracted, a newpallet 12(a) carrying front curve lens mold portions from conveyor 27 ispositioned at the vacated first position (indicated by arrow “A”) in themanner described above. Simultaneously therewith, the forward motion ofa pallet 12(b) carrying back curve contact lens mold portions from backcurve supply conveyor 29 is terminated at a position “D” as indicated inFIG. 8(a). The process for aligning a pallet 12(b) carrying back curvelens mold portions at position B is essentially similar as describedabove with respect to pallet 12(a). In a timed manner, clamping jaws149(a),(b) close to clamp pallet 12(b), while the other pallets onconveyor 29 accumulate behind the clamped pallet. The jaws 149(a),(b)are subsequently opened to release the pallet so that the motion of theconveyor 29 pushes the pallet 12(b) in alignment with the second pusherarm 142. The jaws 149(a),(b) are immediately closed to clamp the next ofthe accumulated pallets to prevent its forward motion. Pallet 12(b)carrying back curve contact lens mold portions is now positioned at “D”,immediately adjacent the previously positioned pallet 12(a) from theinitial step, situated at position “C”, with both in alignment with thesecond arm 142. After appropriate sensing, the arms 141,142 of thedouble cross pusher 40 are again caused to slide along track 147 fromtheir original position in the direction indicated by the double headedarrow so that first arm 141 pushes a pallet 12(a) to the second position(“C”) and the second arm 142 pushes the pair of pallets 12(a),12(b) fromsecond position “C and D” to a third position indicated by “E” in FIG.8(a). Finally, the pusher arms 141,142 are raised so that the mountingmeans 145 and the arms may be retracted along track 147 and lowered attheir original position. While the first and second arms 141,142 arebeing retracted, a new set of pallets are being loaded at theirrespective positions. Specifically, a pallet 12(a) is loaded at positionindicated as “B” (FIG. 8(b)) and a pallet 12(b) is loaded at positionindicated as “D” adjacent the previously positioned pallet 12(a) and thesequence is repeated.

While the new set of pallets are being loaded at their respectivepositions, a third pusher arm 144 operable by pneumatic driving means148 is activated to push the adjacently situated pair of pallets12(a),12(b) in the direction indicated by arrow “F” in FIG. 8(a), forengagement with the drive belt 44(a) of sequencing conveyor 32. Insteady state operation, the sequence of events described above isrepeated so that pairs of pallets 12(a),12(b) are sequentiallytransported along sequencing conveyor 32 to the filling and moldassembly stations of the contact lens production facility.

The paired sets of pallets 12(a),12(b) carrying respective front curveand back curve lens molds reach a second sequencing apparatus 52(illustrated in FIG. 8(b)) where their forward motion is diverted forinput to the filling apparatus 50.

FIG. 8(b), which is a continuation of FIG. 8(a), illustrates theprecision pallet handling apparatus 55 for transferring pallets fromsequencing conveyor 32 to the filling apparatus 50. Specifically, themotion of each pallet 12(a),(b) carrying respective lens mold halves isterminated by a pair of upstream clamping jaws 153(a) and 153(b), in themanner as described above, at position indicated as “C” in front ofpusher 154(a) of ram 154. When the motion of the first pallet is halted,the alternating series of pallets 12(a),(b) accumulate therebehind. Thejaws 153(a),(b) are opened to enable one pallet, for e.g., pallet 12(b)carrying back curve lens mold halves, to align with pusher 154(a) of ram154. Then, pusher 154(a) which in the preferred embodiment is driven bypneumatic cylinder unit 154, is timely activated to push the pallet12(b) along slide plate 32(a) for a distance equivalent to the length ofthe pallet in the direction indicated by arrow “H”. This process isrepeated to bring a pallet 12(a) into engagement with pallet 12(b) andboth are advanced in the direction of arrow “J” and to a position inalignment with ram head 157(a) of ram 157. The ram 157, which is servomotor driven is timely activated to first push the pallet 12(b) alongtrack 32(b) in the direction indicated by arrow “J” for a distanceapproximately equal to the width of the pallet ±0.1 mm. This sequence isthen repeated with pallet 12(a). This sequence of events hereindescribed is continuously repeated to push a row of pallets and enableprecision registration of pallets 12(b) and 12(a) when they alternatelyenter filling and dosing apparatus 53 of filling/mold assembly station50.

Filling and Assembly Stations

The filling and assembly station, indicated generally at 50 in FIGS. 2and 8(b) includes three separate stations, including a filling station53, further described and illustrated in FIGS. 10(a), 11 and 15; asurfactant application station 54, illustrated and described withrespect to FIGS. 10(b) and 12; and an assembly station 55, illustratedand described with respect to FIGS. 10(c), 10(d), 13, 14(a), 14(b) and16.

As described briefly above and in further view of FIGS. 10(a) and 11, apredetermined amount of the degassed monomer or monomer mixture 11 isdeposited in a front curve mold half 10 by means of a precision dosingnozzle 242, which is part of the dosing or filling apparatus 53 ofstation 50. The monomer may be dosed in each of the front curve moldhalves, carried in the alternating pallets, under vacuum to avoid thepossibility of entrapping any gasses between the monomer and the frontcurve mold half. The polymerizable monomer mixture is first degassed, asdescribed previously, to insure that dissolved gasses are not present inthe monomer inasmuch as dissolved gasses may well form bubbles as themonomer is released from the relatively high pressure of the dosingnozzle 242 to inert atmospheric, N² or vacuum conditions surrounding thefront curve mold half 10. Additionally the oxygen content of the monomersolution is monitored prior to discharge in the front curve moldcavities.

Each of the nozzles 242 includes a teflon dosing tip with an O.D. ofapproximately 0.070″ and an I.D. of approximately 0.040. Each tip is cutat approximately a 45° angle, and is positioned to be carried within 0.5mm of the horizontal tangent of the front curve 31 surface 15 at thetime of dosing.

As the monomer or monomer mixture is dosed, it pools upwardly around thetip, as illustrated in FIG. 11(a), so that the angle of the tip iscovered. When the manifold assembly 251 is reciprocated upwardly, thepool of monomer wicks the nozzle tip, and draws any excess on the tip.This wicking action increases the accuracy of the dose, it pulls offpotential drops of monomer and it avoids any agitation of the monomerthat might result in bubble formation.

If drops of monomer form on the tip, there is the possibility ofcontamination of a passing pallet or the dosing station form aninadvertent drop. Individual drops of monomer, even when deposited intoa mold cavity, or on top of the monomer pool, have been found togenerate a “seed” site for a gas bubble. By wicking the tip with themonomer pool, this possibility is substantially eliminated.

In the preferred embodiment of the invention, approximately 60 μl ofpolymerizable monomer or monomer mixture is deposited in the front curvemold half to insure that the mold cavity is overdosed to avoid thepossibility of incomplete molding. The excess monomer is removed fromthe mold cavity in the final step of the demolding of the front and backcurve mold halves as an excess HEMA ring as will be hereinafterdescribed. (When hydroxyethylmethacrylate is used, the excess monomer isreferred to as a HEMA ring).

At station 53, as illustrated in FIG. 11, a plurality of monomer supplylines 241 are coupled to associated discharge nozzles 242, two of whichare illustrated in FIG. 11 which are suspended directly over the path ofthe pallet 12(a) and the individual front curve molds 10. The dosing orfilling station 53 includes a manifold block 251 for receiving each ofthe monomer discharge nozzles 242 and a vacuum seal 252 which may beused to cooperate with the outer perimeter 140 of pallet 12(a) toprovide a sealed enclosure that may be evacuated with a vacuum pump sothat the deposition of the monomer occurs in a vacuum, if desired. Themanifold block assembly 251 reciprocates with respect to a fixedplatform 253 on a pair of tubes or cylinders 254(a), 254(b) as will behereinafter described with respect to FIG. 15. The dosing module 53 alsoincludes a pair of bore scope tubes 255, 256 which enable inspection ofthe monomer dosing, if desired, through an optic bore scope 200, asillustrated in FIG. 15.

As illustrated in FIG. 15, the entire deposition module 53 isreciprocated vertically with respect to a fixed support frame 252 and264 by means of a short stroke pneumatic cylinder 265 mounted betweenframe 262 and drive rod 263(a) of pneumatic cylinder 263 which isfixably mounted to fixed frame 264. Vacuum is supplied through thefilling or dosing station through manifold 266 and vacuum line 267 to aninterior manifold 268 formed in one of the two reciprocating supporttubes 254(a), 254(b). The tubes or cylinders 254(a), 254(b) reciprocatewith fixed guide tubes 257,258. A vacuum plenum is also formed in themanifold block 251 by means of bore holes 269 and 269(a) which providevacuum communication between the vacuum manifold 266 and the interior ofthe dosing station 53 defined by perimeter seal 252 and the pallet12(a).

An optic bore scope 200 is illustrated in FIG. 15 with an optic probe201 extending down into the blind holes 128(a),(b) of pallet 12(a) andmanifold block 251. A dummy or blind 202 is installed in the other borescope tube 256 to seal access into the interior vacuum plenum of theassembly station 53 when a bore scope is not in use.

In operation, a pallet 12(a) is advanced into the dosing station 53 bymeans of the material handling ram 157 previously discussed with respectto FIG. 8(b). Once in position, the manifold assembly 251 isreciprocated downwardly by means of pneumatic cylinder 265. If vacuumdosing is desired, when the vacuum seal 252 on the manifold assembly 251engages the pallet 12(a), the sensor assembly 265 may be triggered,thereby opening a valve to draw a vacuum in manifold 266, vacuum line267, manifold 268 and plenum 269, 269(a). It should be noted that avacuum is not required for filling or dosing of the mold cavities, butdoes avoid the possibility of N₂ gas being trapped between the monomerand the front curve mold half. It should also be noted that the ambientatmosphere surrounding pallet 12(a) is a low oxygen N₂ environment andevacuation of the chamber is an evacuation of the N₂ gas. After vacuumhas been established within the dosing chamber, pumps 440 (illustratedin FIG. 9) are actuated to deliver a precise dose of 60 μl to each ofthe mold cavities 10 illustrated in FIG. 10(a) and 11.

After the monomer has been dosed into the individual mold cavities, thevacuum is broken in manifold 266 and the manifold assembly 251 isreciprocated upwardly by pneumatic drive means 265 to draw dosing nozzle242 out of the monomer pool 11 and allow transport of the pallet 12(a)to the apparatus 54 which coats the mold flange 18 with a mold releasesurfactant. Pneumatic cylinder 263 may be used to lift the assemblymanifold 251 to a high service position for cleaning and servicing.

Surfactant Application

As illustrated in FIG. 12, a surfactant is applied to the mold flange 18by a stamping station 54 includes a frame structure 222 having a supportmember or base 224 on which there are positioned a plurality of spacedupright guide columns 226. These columns have slide members 228 thereonfor supporting components for a stamping station 54 so as to bevertically displaceable along the guide members. The stamping station 54is mounted for vertical reciprocation proximate the upper end of thecolumns through the intermediary of suitable guide bushings 234 and theslide members 228, and wherein the vertical displacement is implementedthrough suitable actuating or drive unit 237 which is not described infurther detail herein, and which, if desired, may be operated from asuitable control and sensor unit 236 on base 224.

The stamping station 54 includes mounted thereon a plurality of stamps238 each adapted to be moved in vertical reciprocatory movement in acoordinated manner in conjunction with the stamping station 54, whereinthe number of stamps 238 is correlated with the number of front curves18 located in the mold depressions 130(b) formed in the mold pallet12(a). Each stamp 238 consists of a composition of about 90% urethaneand 10% silicone in at least the portions thereof which are adapted tocontact the flanges 18 of the front curves 10 on the mold pallet 12(a).

Adapted to be positioned in spaced relationship below the lower end ofeach stamp 238 of the stamping station 53 when the latter is in a raisedposition, is a horizontally shiftable pad member 240. The pad member 240is basically a cushion which is constituted of a suitable porousmaterial, such as porous polyethylene having an average 10 micron poresize, and which is impregnated with a solution containing a surfactant,the latter of which may be present in a highly concentrated state. Thelower surface of the stamping pad member 240 is supported on a base240(a) consisting of a liquid-impervious material. The upper surface ofthe pad member 240 is covered by a filter 244, preferably of nylon,having a mesh size of 1.2 microns so as to act as a metering device andallow only relatively small quantity of surfactant to pass therethroughas the surfactant is wicked from the bottom of the pad member 240 to thetop upon the pad member being pressingly contacted by the bottom ends ofthe stamping heads 238, as described hereinbelow.

The stamping pad member 240 is supported on a horizontally shiftablecarriage structure 241 which is operable at a predetermined elevationbelow the lower ends of the stamps 238, so as to be horizontally movableinto position below the stamps 238 between the upright guide columns 226or, alternatively, moved outwardly thereof when not needed. Thehorizontal shifting motion may be imparted to the carriage 241 and,resultingly, to the pad member 240, by means of a suitable actuatingcylinder which is operatively connected with the carriage 241.

The foregoing carriage 241 is located at an elevation or height abovethe mold pallet track 223, along which mold pallets 12(a) or 12(b) areadapted to be sequentially advanced into position below the stampingstation 53 in order to enable the stamps 238 to apply a thin film orcoating of surfactant to the surfaces 18(A) of the front curves 10positioned thereon before being transported further in connection withthe forming of the contact lenses.

Operation of the Surfactant Apparatus

In order to facilitate the deposition of a thin film layer of surfactantonto the surfaces 18 of the front curves 10 on the mold pallet 12(a)which has been positioned below the stamping station 53, the stampingstation is maintained in a fully raised position on guide columns 226.This is implemented by means of a lifting cylinder 237 acting on slidemembers 228 vertically movable along the guide columns 226. The extentof vertical movement may be controlled by a suitable control and sensorarrangement 236. The pad member 240 is interposed in spaced verticalrelationship between a pallet 12(a) and the lower ends of the stamps 238on the stamping station 53. The interposition of the pad member 240 iscarried out by shifting the carriage 241 horizontally so as to locatethe pad member 240 beneath the stamps 238. Thereafter, the stampingstation 230 is actuated so as to cause the stamps 238 to be displaceddownwardly into contact with the upper surface of the filter 244 on thepad member 240, whereby a small amount of surfactant is expelledupwardly through the nylon filter 244 to coat the lower downwardlyfacing surface of each stamp 238, forming a thin layer or coating of thesurfactant thereon.

The surfactant with which the pad member 240 is impregnated may be asolution with an almost 100% concentrated strength of surfactantdispersed therein so as to enable forming a layer thereof on thetherewith contacting surfaces of the stamps 238. Preferably, thesurfactant is constituted of Tween 80 (registered trademark); i.e. aPolysorbate 80. This is basically polyethylene oxide sorbitanmono-oleate or the like equivalent, and consists of an oleate ester ofsorbitol and its anhydrides copolymerized with approximately 20 moles ofethylene oxide for each mole of sorbitol and sorbitol anhydrides.

In order to ensure that a uniform layer or very thin film of thesurfactant is deposited on the surfaces 18 of each of the front curves10 which are located on the old pallet 12(a), each stamp 238 isindividually resiliently mounted through the provision of a suitablebiasing spring 245, preferably such as encompassing coil springs whichare supported in the stamping station 54, ensuring that notwithstandingmanufacturing tolerances, a uniform pressure will be subsequentlyexerted by the stamps against all contacting flanges 18 on the frontcurves 10 which are located on the mold pallet. hereafter, upon thesurfactant being wicked up through the pad, expelled through the nylonfilter 244 and deposited on the lower surface of each stamp 238, thestamping station 54 and stamps 238 are raised vertically, and thestamping pad member 240 with its carriage 241 is moved horizontally outof the stamping station from its position between the guide columns 226,thereby opening the space between the stamps 238 and the therewithaligned front curves 10 on mold pallet 12(a). Thereafter, the stampingstation 54 is again shifted downwardly along the vertical guide columns226 until the stamps 238 have their surfactant-wetted lower end surfacescontact the surfaces 18 on the front curves 10, thereby depositing athin layer or film of the surfactant thereon, with such layer being at auniform thickness on each respective front curve surface 18 due to theresilient biasing forces being exerted by each of the springs 245 actingon the individual stamps 238.

Thereafter, the stamping station 54 is again moved vertically upwardlyalong guide columns 226, and a subsequent molding pallet 12(b) mountingback curves 30 is advanced through the stamping station of theapparatus. This time period enables stamps 238 to be recoated withsurfactant from the shifting stamp pad member 240.

The molding pallet 12(a) which has the front curve surface thereonalready treated with the surfactant is advanced out of the stampingstation so as to be mated with base curves 30. The process may then berepeated with the subsequently introduced front curves 10 on moldpallets 12(a) in the same continuous manner.

The foregoing structure enables the deposition of a thin and uniformlayer or film of the surfactant onto specified surfaces 18 of the frontcurves 10 so as to enable easier subsequent separation of the basecurves 30 therefrom and removal of the HEMA-based ring material with theback curve 30. This avoids the step of manually removing the remnants ofthe HEMA rings, excessed during the molding of the hydrophilic polymercontact lenses, and avoids contamination of the final package or theproduction line equipment that results from inadvertent error inherentin manual operations.

As illustrated in FIG. 5, a complimentary pair of front 10 and back 30curve mold halves define the mold cavity and the shape of the finaldesired lens 8. After the dosing step in the filling apparatus 53, inwhich the front concave mold half 10 is substantially filled with apolymerization mixture 11, the concave front mold half 10 is coveredwith the back curve mold half 30 under a vacuum to ensure that no airbubbles are trapped between the mold halves. The back curve mold half isthen brought to rest on the circumferential edge 14 of the concave frontmold half to sever the incipient lens from the excess monomer, to ensurethat the resultant lenses are properly aligned and without distortion,and to form a mold assembly 39 which includes both mold halves and theincipient lens 101. The provision of tabs 26 and 37 extending fromrespective sides of each front and back curve mold halves are preferablypositioned one over the other as shown in FIG. 5 during the moldassembly, to facilitate handling thereof, and to facilitate the pryingapart of the halves after the polymerization. The tabs may also be usedto provide torric orientation of the lens, since the orientation of tab26 on the front curve mold half is fixed by recess 130(c), while the tab37 may be subsequently aligned to provide torric differentiation in theoptical characteristics of the lens.

The excess monomer or monomer mixture displaced from the mold cavity 101forms a HEMA ring 13, which preferentially adheres to the underside offlange 36 of back curve mold half 30 by reason of the surfactant coatingon flange 18 of the front curve mold half 10.

Mold Assembly Apparatus

The operation of the assembly station of the present invention will beexplained with reference to FIGS. 10(c), 10(d), 13, 14(a), 14(b) and 16wherein FIG. 14(a) represents an external elevation view of the assemblymodule 55 and FIG. 14(b) represents a partially cross-sectioned view ofthe assembly module 55 that is sectioned along two separate axes fromsection line A-A′ for the purposes of illustration.

The assembly of the mold halves is also described in the chartillustrated in FIG. 13 in which the position of a reciprocating assemblypiston 271 is plotted as a function of time. As illustrated at the zerostart point, the reciprocating piston 271 begins to descend for the backcurve pick up, and reaches and secures the back curve 30 inapproximately 0.25 seconds. The piston 271 is then reciprocated upwardlyto its upper position 14 mm above pallet 12(b) in approximately 0.25seconds. Then, the pallets are advanced wherein the back curve mold halfpallet 126 is removed and the front curve mold half pallet 12(a) isinserted, which transfer takes approximately 0.5 seconds. While thepallets are being transferred, a vacuum chamber begins its descenttowards the front curve mold pallet 12(a) and contacts the mold palletto establish a seal between the chamber and the pallet as will behereinafter more fully described with respect to FIG. 14(b). A seal isestablished at approximately 1.25 seconds after the zero point, and thenitrogen in the chamber is then evacuated until a vacuum equilibrium isreached at approximately 1.75 seconds.

It should be noted that the reciprocating piston 271 is carried withinthe vacuum chamber so that as the vacuum chamber descends and seals tothe pallet, the reciprocating piston 271 and the back curve mold half 30have been partially lowered to approximately 5 mm above the front curvemold half. At 1.75 seconds, the reciprocating piston 271 beginsindependent downward travel and contacts the pool of monomer 11 atapproximately 2.5 seconds after the zero point. Downward travel of thereciprocating piston continues and at approximately 3 seconds, the backcurve mold half is firmly seated on the parting edge 14 of the frontcurve mold half indicating formal assembly. Shortly thereafter, thevacuum in vacuum passageway 294 is broken, but the reciprocating piston271 maintains a downward force on the back curve mold half while theremainder of the assembly module continues a downward travel to therebyestablish an independent floating clamping of the back curve mold half30 against the porting edge 14 of front curve mold half 10. As will behereinafter explained, this clamping or “over travel” step is optional.At approximately 3.4 seconds, the vacuum is broken in the vacuum chambersurrounding the mold assemblies and at approximately 4.4 seconds thereciprocating piston 271, the vacuum chamber and the assembly module 55begin to retract. At 4.75 seconds, the pallet 12(a) containing theassembled mold halves is transferred out of the assembly station, and anew pallet 12(b) containing the back curve mold halves is inserted underthe assembly module 55. At approximately 5 seconds, the reciprocatingpiston 271 is then moved to its back curve pick up position, and at 6seconds, the assembly beings anew at the zero start point.

The assembly station 55 includes 4 reciprocal pistons 271, two of whichare illustrated in the left section of A-A′ of FIG. 14(b) with hackcurves attached thereto and two of which are partially visible in theright hand section of A-A′ of FIG. 14(b) without back curves. It shouldbe understood that reciprocating pistons are used for the pallets having8 sets of front and back curve mold halves. The reciprocating pistons271 are mounted for reciprocation within the vacuum housing 272 and areboth carried by and may float within the primary housing 273. Each ofthe three members 271, 272 and 273 reciprocate at various times, bothwith respect to each other and with respect to the pallet 12(b) and thepallet 12(a) containing front mold curves.

With reference to FIGS. 14(b) and 16, the vacuum manifold housing 272and the primary housing 273 are mounted for reciprocal movement oncylinders or tubes 274,275 and reciprocate with respect to stationaryframe member 276 in response to servo motor 277 which raises and lowersa reciprocating support platform 278. Drive motor 277 is fixablyattached to frame member 276 by means of guide tubes 279 and 280 andcross-member 281. Thus, the stationary frame member 276, guide tubes279,280 and cross-member 281 provide a box frame that is stationary withrespect to the reciprocating members of the apparatus. Pallet guiderails 282 are also provided for each pallet 12(a),(b) entering theassembly stations which are advanced by means of the material handlingpusher 157 previously described and illustrated with respect to FIG.8(b). Guide rails 282 are also fixed with respect to the stationaryfixed platform 276.

As illustrated in FIG. 14(b), the vacuum manifold housing 272 and theprimary housing 273 reciprocate with respect to each other with thevacuum manifold housing 272 being biased downwardly by a pair of springmembers 283,284 positioned on opposite sides of the respective housings.The vacuum manifold housing 272 is secured to the primary housing 273 byvirtue of a pair of bolts 285,286, one of which is illustrated incross-section in FIG. 14(b) at 285, which are free to reciprocateupwardly into recesses such as recess 287 formed in the primary housing.Likewise, the reciprocating pistons 271 and reciprocating manifoldmembers 288,289 also provide reciprocating guides and support betweenthe two housing members 272,273.

A pair of bore scope housings 290 and 291 provide access for a borescope 200 and an optic probe 201 which may be inserted into the assemblycavity for viewing or quality control purposes. When not in use, thebore hole housings 290,291 are closed by a blind 202 in order to allow avacuum to be drawn within the assembly housing.

In operation, a pallet 12(b) containing mold half back curves isadvanced under the reciprocating pistons 271 as illustrated in FIG.10(c). When the pallet 12(b) is in position, the assembly module 55 isreciprocated downwardly by pneumatic drive motor 277 and cross-member278 and the reciprocating tubes 274,275 to draw both the vacuum manifoldhousing and the primary housing downwardly. The vacuum manifold housing272 is biased in its downward position by means of springs 283,284 andthe individual reciprocating pistons 271 are biased downwardly by virtueof their mounting within the vacuum manifold housing 272, and by virtueof air pressure maintained within the pneumatic cylinder 293 mounted inupper portion of the primary housing 273. Within approximately 0.25seconds, the reciprocating pistons 271 have engaged the back curve moldhalves 30 on pallet 12(b) and a vacuum is drawn through vacuum manifoldin reciprocating piston 271, which has radial bores 294 (FIG. 10(c))which communicate with an annular chamber 295 formed in the vacuummanifold housing 272, two of which are illustrated in FIGS. 14(b) and16. Each of these annular chamber passageways 295 is interconnected toeach other and a common plenum (not shown) that extends across all 4annular manifolds 295 on one side of the vacuum manifold housing 272.

A pair of reciprocating vacuum manifolds 288,289 connect the vacuummanifold 272 with the primary manifold 273, with one of the tubes 288,illustrated in cross-section in FIG. 14(b). The vacuum manifold 288reciprocates in bore 298, while vacuum manifold 289 reciprocates in asimilar bore (not shown). These reciprocating manifolds are essentiallyidentical, except that they supply vacuum at two different pressures totwo different parts of the assembly module.

As the assembly module reaches its lower most point of travel, each ofthe back curves 30 is removed from the back curve mold pallet 12(b) bythe vacuum drawn in the reciprocating pistons 271. The entire assemblymodule 55 is then reciprocated upwards in approximately 0.25 seconds toenable transport of the empty pallet 12(b) along conveyor 32(b) out ofthe assembly module and the insertion of a new pallet 12(a) that isfilled with front curve mold halves, each one of which has been dosedwith a monomer at the filling module 53. Pallet 12(a) is advanced intoposition as illustrated in FIG. 10(d) but is registered in preciseposition by means of tapered registration pins 306,307 which cooperatewith the blind registration holes 129(a),129(b) formed on pallets 12, asillustrated in FIG. 7(a). The taper on pin 306 is sufficient to registerthe pallet within ±0.1 mm for the purposes of precision assembly of themold halves.

The assembly cycle begins by reciprocating both the vacuum manifoldhousing 272 and the primary housing 273 downwardly until a perimeterseal 310 contacts the outer perimeter 140 of the pallet 12(a). Ascontact is made with the perimeter seal, a vacuum switch is actuated bymeans of a proximity switch adjacent to reciprocating cross-head 278which actuates a second vacuum source which draws a vacuum throughvacuum tube 311 and the interior of reciprocating drive tube 274 toevacuate the chamber formed between the vacuum manifold housing 272 andthe platform 276.

It should be noted that the vacuum drawn in the two reciprocating drivetubes 274,275 is slightly different, with the vacuum drawn in the tube275 being slightly greater than that drawn in tube 274 in order toinsure that the back curves are retained on the reciprocating pistons271 prior to their deposition on the monomer and the front curve moldhalf. In the preferred embodiment, the pressure drawn in the vacuummanifold around the pallet 12(a) is on the range of 5 to 7 millibarswhile the vacuum drawn within the reciprocating pistons 271 is on theorder of 3 to 5 millibars.

After the vacuum has been established in the vacuum manifold housing272, the vacuum manifold housing ceases to reciprocate and remainsstationary with respect to the pallet 12(a). However, the upper orprimary housing 273 continues to reciprocate downwardly enabling theback curves to contact the monomer and slowly displace it outwardly tofill the mold cavity as the two mold halves are assembled. The vacuummaintained around the housing enables the assembly of the two curves ina more rapid and expeditious manner than if assembled under ambient N₂pressure. When assembled under vacuum, the deposition speed may reach ashigh as 5 mm per second, whereas without vacuum, any speed greater than1 mm per second may result in undue agitation of the monomer and thecreation of bubbles which affect and impair the quality of the resultantlens. Thus, an assembly step which requires 6 to 9 seconds inatmospheric pressure can be accomplished in 1 to 2 seconds. Further, ifa vacuum is not drawn, it is possible for nitrogen to be trapped betweenthe mold halves or between the monomer and the back curve therebycreating another bubble or puddle which will result in rejection of thatlens.

Independent travel of the two manifolds 272,273 is provided since thevacuum manifold housing 272 no longer reciprocates downwardly after itis seated on pallet 12(a). However, the upper primary housing continuesto reciprocate downwardly depositing the back curve mold half, andcontinuing on to thereby completely compress springs 283 and 284. Asthese spring members are compressed, the reciprocating pistons 271 floatbetween pneumatic cylinders 293 which have been pressurized to apredetermined pressure and the back curve mold half 30. Thus, the finalclamping pressure on the back curve mold member is determined by the airpressure maintained in pneumatic cylinders 293, and not by springmembers 283,284, or the pressure generated by drive motor 277. Thisenables independent reciprocal movement or floating movement of each ofthe reciprocal pistons 271, while enabling all of the pistons to bepressurized to a common predetermined value. Thus, misalignment of asingle mold part will not destroy the entire batch of mold assemblies onpallet 12(a).

The clamping pressure firmly seats the back curve mold half 30 on thefront curve mold half 10 and seats the convex portion 33(a) of the mold30 against the parting edge 14 formed on the front curve mold half 10thereby severing the monomer in the lens blank 8 from the monomer in theHEMA ring 13. After the mold halves have been seated, the vacuum in eachof the reciprocating pistons 271 is first broken by opening a valve invacuum line in 304. Shortly thereafter, and after an optionalpredetermined clamping period and a predetermined clamping pressure, thevacuum between the vacuum manifold housing and the pallet 12(a) isbroken by opening a valve in vacuum line 311. Typically the period is0.5 to 3 seconds, but preferably is 1.5 seconds. The clamping pressuremay range from 0.5 to 2 Kg/per lens but preferably is 1 Kg/per lens.Thereafter, drive motor 277 is actuated and the entire assembly module59 is raised upwardly and reset for a new back curve pickup and a newcycle of operation. In the event the optional clamping movement is notprovided, the resilient biased pistons 271 may be fixably mounted invacuum manifold 272 and reciprocates downwardly to seat the back curvewell into the monomer, but 0.1-0.2 mm from sealing engagement with theparting ring 14. In this embodiment the optional clamping step may alsobe provided in the precure step. When seated in this manner under vacuumconditions, with a completely filled mold cavity sealing the mold halvestogether, atmospheric pressure will “clamp” the mold halves together at14.7 psi when the vacuum in the vacuum manifold 72 is broken.

As illustrated in FIG. 8(b), after exiting the mold assembly module 55of apparatus 50, the pallets 12(b) that had transported the back curvelens mold portions are empty and are recirculated back to the supplyconveyor 29 to pick-up a new set of back curve lens molds from theinjection mold 102(a). To accomplish this, ram assembly 155 having areciprocating ram head 156 is enabled to push the empty pallet 12(b)from the exit of module 55 in the direction indicated by arrow “K” wherethe back curve supply conveyor 29 picks up the pallet 12(b) forrecirculation at the back curve lens mold pick up point. Additionally,as shown in FIG. 8(b), a second reciprocating ram 155′ and ram head 156′is provided to push, in the direction indicated by arrow “L”, a pallet12(a) containing front curve lens molds back to the front curve supplyconveyor 27. This is done only if the line quality control systemindicates that a pallet 12(a) contains a lens mold assembly having moldhalves that are misaligned, that are not seated correctly in a palletrecess or are out OL specification in some manner. Detection of errorsmay occur at a variety of locations in the production line, including orat the filling and mold assembly stations and the pallets are flagged bycontrol means (not shown) so they may be rejected by ram 155′ forrecirculation. The contact lens production line facility includes asuction vent apparatus for removing the mold assemblies from therejected pallet 12(a) while being recirculated back to or while on frontcurve supply conveyor 27.

As shown in FIG. 8(b), the individual pallets 12(a) containing the eightcontact lens mold assemblies leave the filling/mold assembly apparatus50 on conveyor 32(c) at a rate of 12 mm/sec before entering the precureassembly 60 where the front and back curve mold halves are then clampedtogether in the precure step.

As will be explained below, while the mold halves are clamped underpressure, the polymerization mixture is then exposed to actinic light,preferably from a UV lamp. Typically the mold halves are clamped forapproximately 40 seconds with 30 seconds of actinic radiation. At thecompletion of the precure step, the polymerization mixture has formed apartially polymerized gel, with polymerization initiated throughout themixture. Following the precure step, the monomer/solvent mixture is thencured in the UV oven apparatus 75 whereby polymerization is completed inthe monomer(s). This irradiation with actinic visible or ultravioletradiation produces a polymer/solvent mixture in the shape of the finaldesired hydrogel lens.

In the preferred embodiment of the present invention, two separatedevices are illustrated for transport of the pallets 12(a) within theprecure apparatus 60.

A first transport mechanism is described with respect to FIGS. 8(b), 17,19 and 20 while a completely different mechanism is illustrated in FIGS.21 and 22. The method employed by each is essentially the same, in termsof the clamping action and actinic exposure and differs only in theapparatus used to effect the handling of the pallets.

As illustrated in FIG. 8(b), the conveyor 32(c) delivers pallets 12(a)containing a plurality of molds to an accumulating section generallyindicated as 168 which assembles a plurality of pallets for a batchoperation at the precure assembly 60. Accumulator section 168 includes aholding mechanism 166 that is timed by a control means (not shown) tohalt a lead pallet in place on the conveyor 32(c) and enable apredetermined number of subsequent pallets to assemble behind the haltedlead pallet to enable batch processing at the precure apparatus. In thepreferred embodiment, twelve pallets are accumulated enabling up toninety-six (96) mold assemblies to be processed at the precure apparatus60 in a batch mode for an extended period of time of 30 to 60 secondswhile continuously receiving new pallets from the production line at therate of 1 every 6 to 12 seconds.

As shown in FIG. 8(b), lead pallet 12(a′) is halted behind holdingmechanism 166 while the rest of the pallets accumulate therebehind. Upto twelve pallets are being processed in the mold clamping and precureassembly 60 while the new set of pallets are being accumulated inaccumulating section 166, thus, assuring a continuous flow of palletsinto the precure assembly.

After accumulating up to twelve pallets in accumulating section 168,holding mechanism 166 is retracted and the batch pusher arm 173 isextended to align the twelve pallets on the conveyor 32(c) convenientlywithin arms 171(a),171(b). It is understood that a suitable trackmechanism 175 and driving means (not shown) is provided for enablingbidirectional and orthogonal horizontal movement of batch pusher arm173. Once the 12 pallets are aligned between arms 171(a),(b) of batchpusher arm 173, the pusher arm is driven in the horizontal directionindicated by arrow “M” as shown in FIG. 8(b). The previous set of twelvepallets that had been undergoing mold clamping and precure aresimultaneously pushed out of the precure assembly 60 by the arm 171(b)of batch pusher 173 as the new sets of pallets are brought in by thebatch pusher 173. In the partially exposed view of the UV polymerizationoven in FIG. 8(b), six (6) of the previous set of pallets have beenpushed onto a conveyor 31(b) in the curing apparatus 75 thus, dividingthe set into two batches of six pallets each for UV polymerization asdescribed hereinbelow.

As shown in FIG. 8(b) after a new batch of twelve pallets are broughtinto precure apparatus 60 for mold clamping and precure, the batchpusher arm 171(b) is retracted back in the direction of arrow “N” andthe batch rain assembly 176 of batch switching apparatus 45 issimultaneously extended to push the other six pallets of the previousbatch to an entry area 177 where the six pallets will be pushed on to asecond conveyor 31(a) for transport into the UV cycling polymerizationapparatus 75.

FIG. 17 illustrates a side elevation view of one embodiment of theprecure apparatus 60. As illustrated in FIG. 17, the precure apparatusreceives a plurality of pallets having a plurality of contact lens moldstherein, from the infeed conveyor 32(c). The infeed conveyor 32(c)delivers the pallets 12(a) and mold assemblings 39 to the precurestation in an optional low oxygen environment, which environment may beaccomplished by pressurizing an enclosure 326 with nitrogen gas. Priorto polymerization, the monomer is susceptible to oxidation from oxygenwhich results in degradation of the resultant lens.

The precure assembly 61 of the precure apparatus 60 is partially visiblein the breakaway portion of FIG. 17 and more fully illustrated in FIGS.19 and 20. As explained in further detail in co-pending U.S. patentapplication Ser. No. 08/257,792 entitled “Mold Clamping and Precure of aPolymerizable Hydrogel” assigned to the same assignee as the instantinvention, the assembly is raised and lowered into engagement withpallets containing contact lens molds by virtue of a pneumatic cylinder320 which raises and lowers an intermediate support beam 321 andreciprocating shaft members 322 which are journaled for reciprocatingsupport in member 323. After the precure operation, the pallets aredischarged through a nitrogen ventilation and lock mechanism 324 forsubsequent cure by heat and cycled actinic radiation in the UVpolymerization apparatus 75 as will be explained in further detailbelow.

FIGS. 18(a) and 18(b) are diagrammatic representations of alternateembodiments of the precure apparatus 60. Each embodiment of assembly 61includes multiple vertical reciprocal movements for an optional clampingstep, a first one of which is illustrated in FIG. 18(a) in response tomovement from air cylinder 320 and reciprocating beam 321. As theprecure apparatus is lowered along the axis illustrated by arrow “A”, aplurality of annular clamping means 340 will engage the upper annularflange 36 of each of the mold assemblies carried within pallets 12(a).The plurality of annular clamping means 340 are mounted on and travelwith a reciprocating platform 61 of the apparatus, and are resilientlymounted therein for a second parallel reciprocal movement along thedirections of arrow “B” illustrated in FIG. 18(a).

In the practice of the invention, the clamping force may be generated byatmospheric pressure, on the outside of mold halves assembled undervacuum, by an “over travel” clamping apparatus as previously describedwith respect to assembly module 55, by the optional clamping apparatusin the precure station 60, or by all of the foregoing, in combination.

As illustrated in FIG. 18(a), the optional clamping means 340 are biasedwithin frame 352 by springs 312 (illustrated diagrammatically) which maybe an air spring 312(a) (FIG. 18(a)) or a helical spring 312(b) (FIG.18(b)) or may be generated by the physical mass of the clamping member.As the apparatus is lowered, the clamping means 340 will engage andclamp the first and second mold halves together with a force determinedby the spring means 312. When air springs are used, the force will bedetermined by the amount of air pressure provided to the air chamber312(a) by air pressure means 72. While clamping means 340 have beenillustrated as two annular members in FIGS. 18(a) and 18(b) forillustrative purposes, it is understood that in the embodimentillustrated in FIGS. 17, 19, 20, 21 and 22 there are 96 individualannular clamping means, with an individual clamping means for each ofthe mold assemblies 39.

Positioned above the clamping means are a plurality of actinic lightsources 314 which may be UV lamps. A pyrex glass plate 395 separates theprecure area from the actinic light sources 314. This glass plateenables cooling of the actinic light sources 314, while maintaining themold assemblies at a temperature ranging from ambient to 50° C. It alsoprotects the actinic light sources 314 from emissions from the monomers.After the clamping means has engaged the mold halves to clamp themtogether, a shutter mechanism 315 is opened by an air cylinder to enablethe actinic light source 314 to initiate polymerization of thepolymerizable composition in each of the mold assemblies 39. Shutter 315has a plurality of openings 313 defined therein and is reciprocal alongthe X axis (indicated by arrow “C” in FIG. 18(a)) in order to open andclose exposure passage ways 347. The embodiment of FIG. 18(b) isessentially similar to the embodiment of 18(a) with respect to thelocation of light source 314 and shutter 315, and the way they exposethe mold assemblies to actinic radiation.

The operation of the precure apparatus 69 is set by a control circuit,indicated at 310, which controls the duration of the clamping period bythe length of time air cylinder 320(a) is activated to its reciprocaldown position. The control circuit also controls the amount of radiationreceived by the molds controlling the duration of the exposure periodthrough operation of shutter 315 and the air cylinder 346. The intensitymay also be manually adjusted by raising or lowering the lamps 314 withrespect to mold assemblies 39.

The amount of force applied by clamping means 340 may be varied fromapproximately 0.5 Kgf to 2.0 Kgf per lens or mold assembly 39, bypneumatic controller 372, and is applied to keep the flange 36 of theback curve mold half parallel to the flange 18 of the front curve moldhalf for the duration of the exposure. The clamping weight is appliedfor 10 to 60 seconds, but typically for a period of 40 seconds. Afterapproximately 10 seconds of weight, actinic radiation from UV lamps 314is applied to the assembled mola and the polymerizable monomer ormonomer mixture. Typically, the intensity of the UV light source is 2-4mW/cm², and this intensity of light is applied tor 10 to 50 seconds, butin the preferred embodiment, is applied for 30 seconds. It should alsobe understood, that in a batch mode, the cure could proceed tocompletion, to eliminate the cure ovens 75. It is understood thatdifferent intensities and exposure times could be used, including pulsedand cycled high intensity UV on the order of 10 to 150 mW/cm² withexposure times running from 5 to 60 seconds.

At the end of the radiation period, the shutter 315 is closed byreciprocating it to the right as illustrated in FIG. 18(a) and theweight is removed by energizing cylinder 320 to lift the precureassembly 61 upwardly by means of push rods 322. As the assembly 61 islifted, the clamping means 340 will be lifted clear of the molds andpallets to enable the batch pusher arm 173 transport them out of theprecure means as described above to conveyors 31(a),(b) for transportthrough the cure ovens. During the precure time, the temperature in thesystem may be varied from ambient to 50° C.

At the conclusion of the precure process, the monomer has gone throughinitiation and some degree of polymerization. The resultant lens is in agel state with some areas of the lens that have the least thickness,i.e., the edge, having a higher degree of polymerization than the body.The clamping and precure of the edge, under pressure, results in acleaner and more evenly defined edge for the final lens product.

FIGS. 17, 18(a) and 21, 22 depicts a second embodiment for the batchhandling of pallets 12(a) at the precure station. As described abovewith respect to FIGS. 17, 18(a) and 19, 20, the first embodimentreciprocated the UV lamps and clamping members into and out ofengagement with the mold assemblies 39 and pallets 12(a) carried byconveyor means 32(c). In the embodiment illustrated in FIGS. 18(b) and21, 22, the UV lamps are stationary, and the pallets 12(a) are liftedfrom a roller conveyor 32(e) into engagement with the clamping means forthe precure period. Additionally, in the first embodiment, the conveyorsystem splits the line into two lines 31(a),(b) following precure, whilein the following precure embodiment, two separate lines have alreadybeen formed.

The clamping means utilized by the embodiment illustrated in FIGS. 18(b)and 21, 22 utilizes the clamping means 340 previously described withrespect to FIG. 18(b). In this second embodiment, a plurality ofclamping means 340 are mounted above a roller conveyor 32(e) illustratedin side view in FIG. 18(a) by rollers 32(e). A plurality of liftingstandards 381 are positioned between groups of rollers 32(e) on centersapproximate the width of the pallets 12(a). In FIG. 22, a first row ofpallets 12(a) is depicted resting on rollers 32(e) with adjoining edgesof each of the pallets aligned along the top of the lifting standards381.

The pallets 12(a) are aligned in position by means of stop means 383which is lifted by air cylinder 382 during the loading of the precureapparatus. During loading of the device, the stop means 383 isreciprocated upwardly, and the requisite number of pallets 12(a) areadvanced into the precure apparatus. When 6 pallets in each row havebeen advanced, a second stop means 384 is lifted by air cylinder 385 todefine a limit on X axis travel as illustrated in FIG. 22. A separateair cylinder 387 is used in cooperation with stop means 384 to align theadjoining edges of the pallets 12(a) above the centers of the liftingstandards 381. After the pallets have been aligned, the liftingstandards 381 are reciprocated upwardly by means of intermediate supportframe 388 and a pneumatic motor generally indicated as 390.

The pallets arc reciprocated upwardly to the position illustrated at12(a′) in FIG. 18(a), in which position they engage the clamping member340 as previously described. Each of the clamping members 340 alsoinclude a separate independent and resilient spring 312(b), as describedin aforementioned co-pending patent application entitled “Mold Clampingand Precure of a Polymerizable Hydrogel” for driving clamping member 340and the upper mold half 30 (back curve) against the lower mold half 10(front curve) during the precure period.

After the pallets and mold halves have been raised by air cylinder 390and the first and second mold halves clamped together by means ofclamping means 340, a reciprocating shutter 315(a) is shifted asillustrated in FIG. 18(a) to align a plurality of openings therein withthe central openings formed in the clamping means 340 and thereby enableexposure of the monomer in the mold halves by means of actinic lightsources 314 as described generally above with respect to FIG. 18(a). Apyrex glass plate 395 separates the actinic light sources from theprecure area. The clamping period and the amount of exposure toradiation are controlled by a control means in the manner previouslydescribed.

Following the precure of the monomer in mold assembly 39, the pallets12(a) are reciprocated downwardly to the roller conveyor illustrated inFIG. 17 as 32(e) and advanced by incoming pallets 174 to subsequentconveyors 31(a),(b). The individual pallets 12(a) containing the eightcontact lens mold assemblies then enter the UV-cure and polymerizationassembly 75 on two tracks 31(a),31(b) as shown in FIG. 2. In theUV-polymerization assembly 75, the pallets are conveyed at a rate ofapproximately 5.5 mm/sec.

Lens Cure

A preferred apparatus for carrying out the present invention, asillustrated in FIGS. 8(c) and 23, includes a pair of conveyor means31(a),31(b) for moving pallets 12(a) containing the mold assemblies 39in the direction of the arrow. Preferably, conveyor means 31(a),31(b)includes belts on which the carrier 12(a) carrying the mold assembly 39(or mold assemblies) is carried. A convention control means (notdepicted) such as a variable speed motor is connected to conveyors31(a),31(b) to control the rate at which the conveyor means movercarrier 12(a) through the polymerization zone.

Reference numeral 330 denotes generally a housing for a source whichemits ultraviolet radiation as described herein. The housing 330 isdisposed over both conveyor means 31(a),31(b) so as to span the path ofboth conveyors leaving a space through which the conveyor carriescarrier 12 and mold assembly 39 under the housing. Housing 330 cancomprise one unitary section or can be composed of several discretesections arrayed side by side, as shown as units 331 and 332 in FIG.8(c).

FIG. 23 shows generally, in vertical section, any of units 331,332 ofFIG. 8(c). Each unit preferably has a flat horizontal surface 33 towhich are affixed one or more elongated light bulbs 334 of the typecommercially available for emitting ultraviolet radiation. FIG. 23 showsa single bulb, which is one of a multiplicity of bulbs, which is thepreferred arrangement to use when several ranks of mold assemblies aredisposed side-by-side on the conveyor. The bulbs are arrayed side byside, with their longitudinal axes parallel, and in the units indicatedat 331 those axes are parallel to the direction of travel of the moldassembly and in the units indicated at 332, those axes are transverse tothe direction of travel of the mold assemblies 39. The bulbs are mountedin standard electrical fixtures 335, which hold the bulbs in ahorizontal plane parallel to the conveyor and the mold assemblies. Eachof the ultraviolet bulbs 335 is connected to an electrical control means(not depicted) for supplying suitable electric current to the bulbs foractuating them to emit ultraviolet radiation.

The bulb or bulbs 335 under which the mold assemblies travel have theproperty that the intensity of the ultraviolet radiation (measured as,for instance, Mw/cm²) is different at different points along the length(i.e., along the longitudinal axis) of the bulb. At the regions at eachend of the bulb, the intensity is at or below a first intensity levelwhich, at the given distance from the bulb to the mold assembly, isinsufficient to cause initiation of polymerization of the polymerizablecomposition (which first intensity level may be zero). Between the endsof the bulb there is at least one region within which the intensity ofthe emitted ultraviolet radiation equals or exceeds the minimum levelnecessary, at the given distance from the bulb to the mold assembly, toinitiate polymerization of the polymerizable composition. Duringoperation, as the mold assembly passes along the length of the bulb, theintensity of the ultraviolet radiation that the mold assembly receivescycles at least once from an intensity level insufficient to initiatepolymerization up to a intensity at which polymerization is initiatedand back down to an intensity level insufficient to initiatepolymerization.

Preferably, two or more such bulbs 335 are arrayed end to end inadjacent housings 331 over the path that the mold assemblies travel.Each bulb can then have at least one region emitting radiation ofsufficient intensity to initiate polymerization and flanking regions oflesser intensity insufficient to initiate polymerization. In that way,even if each individual bulb has only one region intermediate its ends,which initiates polymerization, each cycle of increasing and decreasingintensity occurs at least two times, during the passage of a given moldassembly under the series of ultraviolet bulbs. It is preferred thatthree to six, more preferably five, bulbs be employed end to end so asto expose the polymerizable composition to three to six, preferablyfive, cycles of increasing and decreasing ultraviolet intensity.

In addition, a source of heat is provided which is effective to raisethe temperature of the polymerizable composition to a temperaturesufficient to assist the propagation of the polymerization and tocounteract the tendency of the polymerizable composition to shrinkduring the period that it is exposed to the ultraviolet radiation. Apreferred source of heat comprises a duct 336 which supplies warm airunder the mold assembly as it passes under the ultraviolet bulbs. Thewarm air is exhausted through the opposite end of the housing, andmaintained at a controlled temperature of 45° to 70°, with a preferredtemperature that varies from housing to housing as will hereinafter bedetailed. Adjustable air passage ways 337 enable precise adjustment ofthe air flow beneath the conveyors and pallets.

It has been discovered that through careful control of the parameters ofthis operation, as described herein, a superior fully polymerizedcontact lens can be produced which exhibits reproducible successfulproduction within a relatively minor period of time. Without intendingto be bound by any particular theory of operation, the observedperformance of this system is consistent with the proposition that asthe intensity of the ultraviolet radiation increases, polymerization isinitiated at a number of different sites, and that thereafter decreasingthe intensity of the ultraviolet radiation, coupled with exposure to aneffective amount of heat, permits the initiated polymerization topropagate preferentially over the continued initiation of newpolymerization. Then, as cycles of increasing and decreasing ultravioletintensity are repeated, fresh initiation of polymerization occurs evenas the previously initiated polymerization continues to propagate. Inthis way, careful control of the magnitudes of the low and highultraviolet intensity levels, by selection of bulbs ofappropriate-radiation intensities and by adjustment of the distancebetween the bulbs and the mold assemblies with the polymerizablecompositions, and careful control of the rate of change of theultraviolet intensity (by selection of the rate of movement of the moldassemblies past the bulbs and selection of the number of bulbs arrayedend to end and their lengths), produces a polymerized article in whichthere is no residual unpolymerized monomer remaining, while the overalldistribution of polymer chain lengths provides a superior contact lens,and in which the polymerized article fills the mold cavity without anyvoids in the article or between the article and the inner surfaces ofthe cavity.

The method and means of the present invention are further illustrated inthe following exemplification, in which the pallets 12(a) are fed fromthe precure apparatus 60 to a pair of conveyor belts 31(a),31(b) whichtravel the length of the polymerization apparatus.

The pallets move on conveyor belts which pass under a series of sixsmaller housings 331 and three longer housings 332 arrayed side by sideas shown in FIG. 8(c) (only five smaller housings are illustrated inFIG. 8(c)), with each housing after the first holds filled withultraviolet-emitting bulbs. All bulbs are mounted to their respectivehousings to lie in the same plane. The vertical distance from the planeof the pallet to the plane of the bulbs, in the first housing thatcontains bulbs that the mold assemblies encounter, should be about 25 mmto about 80 mm. That vertical distance to the bulbs in the subsequentlytraversed housings should be about 50 to about 55 mm.

A duct similar to 336 blows heated air into each of the spaces under allsix housings, including the first 331(a) that has noultraviolet-emitting bulbs. The preferred temperatures to maintainaround the pallet under each housing are about 49° C. to about 64° C.under the first two housings, and about 49° C. to about 59° C. under theother four.

The rate at which the pallet travels is preferably sufficient so thatthe total time that elapses from the moment that a given mold assemblyfirst enters under the first housing until it emerges from under thelast one is preferably about 300 to about 440 seconds.

By operating in this manner, the mold assembly is exposed to multiplecycles of increasing and decreasing ultraviolet radiation intensity. Ineach cycle, the intensity of the ultraviolet radiation ranges from aboutzero, up to about 3-3.5 mW/cm², and then back to about zero. Since thebulbs are of essentially identical length and the pallet moves at aconstant speed, each cycle in the first six ovens lasts essentially thesame length of time.

The Demolding Station

After the polymerization process is completed, the two halves of themold are separated during a demolding step leaving the contact lens inthe first or front curve mold half 10, from which it is subsequentlyremoved. It should be mentioned that the front and back curve moldhalves are used for a single molding and then discarded or disposed of.

As illustrated in FIG. 8(d), the pallets containing the polymerizedcontact lenses in the mold assemblies exit the polymerization ovenapparatus along two conveyors 31(a),31(b), as described above, and enterinto the demold assembly 90. The pallets are transferred from theirconveyors and positioned along a respective transport carrier 182(a),182(b) of dual walking beam conveyor 180 illustrated in FIG. 28. Asillustrated in FIG. 28, transport carrier 182(a),182(b) comprises aplurality of respective spaced apart push blocks, such as the fourlabelled 184(a),(b),(c),(d), that move horizontally to preciselytransport a pallet containing mold assemblies through the demoldapparatus 90.

FIG. 28 illustrates a partially cut side view of dual walking beam 180showing transport conveyor 182(a). As shown in the FIG. 28, thetransport carrier beam 179(a) is mounted by suitable mounting means 197on track 193 for horizontal reciprocating movement thereupon. Motor 191and suitable drive linkages 192 are provided to precisely control thehorizontal movement of the transport carrier beam 179(a) along the track193 so as to enable push blocks to engage and advance the pallet alongthe carrier rails 183(a),(b). Additionally, as shown in FIG. 28, thecarrier beam 179(a) is retractable in the vertical direction by a seriesof pneumatic cylinders, two of which 190(a), 190(d) are shown in thefigure. The cylinders 190(a),(d) and motor 191 are precisely controlledby control means to simultaneously provide for the reciprocation andretraction of the transport carrier beam.

In the preferred embodiment described in detail above, the transportcarriers of the dual walking beam carries the pallets containing contactlens mold assemblies through the demold apparatus where, preferably, theflange portions of the front curve and back curve mold halves aregripped and pulled away from each other, either in directly oppositedirections or through an angle in a prying sort of motion.

Advantageously, the contact lens mold assembly is first heatedmoderately to facilitate separation of the polymerized article from themold half surfaces. As explained in further detail in co-pending U.S.patent application Ser. No. 08/258,265 entitled “Mold SeparationApparatus” assigned to the same assignee as the instant invention, thedemold apparatus 90 includes means for applying a precise amount ofheat, which may be in the form of steam or laser energy, to the backcurve lens mold portion of the contact lens mold assembly, prior toprying apart the back curve mold half from the front curve mold half bya set of pry fingers that are inserted within the gap formed between theoverlying flange portions of each mold half of the mold assembly.

To position a pallet 12(a) from conveyor 31(a) to transport beam 182(a)of dual walking beam 180, the pallet is first clamped by upstreamclamping jaws 186(a),(b) as shown in FIG. 8(d). In a timed manner undercontrol of suitable control means, the pallet is released and positionedon a pair of carrier guide tracks between a pair of push blocks, e.g.,184(a),184(b) of carrier 182 as shown in FIG. 28, for transport throughthe demolding apparatus 90. In a similar fashion, to transport a pallet12(a) from conveyor 31(b) to transport beam 182(b) of dual walking beam180, the pallet is first clamped by upstream clamping jaws 187(a),(b)(FIG. 8(d)), and then timely positioned on a second pair of carrierguide tracks between a pair of push blocks, similar to 184(a),184(b) ofcarrier 182 for precision transport through the demolding apparatus. Theoperation of transport carrier 182(a) of dual walking beam 180 will nowbe described in further detail with respect to FIG. 28. The transferfrom clamping means 186(a),(b) and 187(a),(b) to the dual walking beamis accomplished by a double armed push assembly 195 having a first arm196 and a second arm 197. It operates in substantially the same way asthe sequencing assembly 40 previously described with respect to FIG.8(a).

As shown in FIG. 28, the transport carrier 182(a),(b) includes areciprocating carrier beam 179(a),(b) having plurality of push blocks184(a),(b),(c),(d), spaced equally apart on the respective carrier beams179(a),(b) at a distance approximately equal to that of the length of apallet. Each carrier beam 179(a),(b) is mounted for horizontalreciprocating movement in the directions indicated by the double-headedarrow “A-B” in FIG. 28 for advancing the pallets 12(a) along respectiveguide tracks through the demold apparatus, and, is additionally mountedfor reciprocating movement in the vertical direction as indicated bydouble-headed arrow “A′-B′”.

Each pallet guide track includes a pair of tracking guide rails orshoulders for mating with respective notches 28(a),(b) of the pallet asillustrated in FIGS. 7(b) and 30. The paired set of shoulders andrespective pallet notches 28(a),(b) keep the pallet precisely aligned asit is being advanced by carrier blocks 184 throughout the demoldapparatus, and, further prevents any vertical movement of the pallet12(a) when the mold assemblies 39 are demolded. The height of a pushblock, e.g., block 184(a), is such that it will engage the edge of apallet when the transport beam 179(a) is vertically reciprocated in thedirection indicated by arrow “A′” when advancing the pallet through thedemold apparatus 90, and, will disengage the edge of the pallet whencarrier beam 179(a) is vertically retracted in the direction indicatedby the arrow “B′”.

As previously described above, with respect to FIG. 8(d), a pallet 12(a)is first positioned on the parallel set of tracks 183(a),(b) between thefirst two push blocks 184(a) and 184(b). To advance the pallet, thetransport carrier beam 179(a) is driven forward in the directionindicated as “B” in FIG. 28, so that push blocks 184(a),(b) engagepallet 12(a) to advance its position along the guide tracks 183(a),(b)from its previous position, to a new incremented position. The amount ofincremented advance varies with the type of demolding apparatusemployed. When the laser demold apparatus (FIGS. 24-27) is employed, thepallets are incrementally advanced to advance an entire pallet length,and then a distance equal to the distance between centers of pairs ofmold assemblies carried on pallet 12(a). This enables the laser demoldapparatus to demold a pair of mold assemblies in each advance, and whenthe last pair is demolded, a new pallet is advanced into position.

When the steam demolding apparatus is employed (FIGS. 30-39) the palletsare sequentially advanced one pallet at a time inasmuch as the steamdemolding apparatus demolds the entire pallet in one step. Immediatelyafter advancing the pallet 12(a), the transport carrier beam 179(a) isretracted in a vertical direction beneath the plane of the carrier rails183(a),(b) so that the carrier beam (and push blocks thereon) mayreciprocate horizontally beneath the pallet to its original position inthe direction “A” as indicated in FIG. 28.

After reciprocating horizontally to its original position, the carrierbeam 179(a) (and push blocks 184(a),(b), . . . etc.) is extendedvertically to its original position where the push blocks 184(a),(b)engage a newly registered pallet 12(a) from conveyor 31(a), aspreviously described with respect to FIG. 8(d). Additionally, the firstpallet 12(a) that had been advanced on carrier rails 183(a),(b) is nowengaged between push blocks 184(b),(c). By continuous reciprocation ofthe transport carrier beam 179(a),(b) of dual walking beam 180, aprecise and continuous flow of pallets through the mold separationapparatus 90 is assured.

Laser Demolding

Heating the back curve lens mold creates differential expansion of theheated mold polymer relative to the cooler lens polymer which shifts onesurface with respect to the other. The resultant shear force breaks thepolymerized lens/polymer mold adhesion and assists in the separation ofmold portions. The greater the temperature gradient between the surfacesof the mold portions, the greater the shearing force and the easier themold portions separate. This effect is greatest when there is maximumthermal gradient. As time continues, heat is lost through conductionfrom the back mold portion into the lens polymer and the front moldportion, and then collectively into the surrounding environment. Theheated back mold portion is, therefore, promptly removed so that verylittle energy is transferred to the polymer lens, avoiding thepossibility of thermal decomposition of the lens.

The present invention discloses in two alternate embodiments, twodifferent ways of heating the back curve and demolding the moldassembly. In the first of these two embodiments, heating the back curvemay be accomplished by use of a source of electromagnetic radiation,preferably a carbon dioxide (CO₂) laser, applied to at least one of themold portions. The laser is preferably of about 80 Watts at a wavelengthof 10.6 μm. The exposure of the mold portion to the laser is between onehalf and one second.

In the case of lasers, both mid-infrared and UV, the laser energy isnearly 100% efficient because the polystyrene mold material is nearly100% absorptive and only a tiny fraction of the incident radiation isreflected or scattered. In this way there is little or no energy lost toatmospheric absorption, so only the sample is heated.

Also, because of the absorptive nature of the mold material at thesefrequencies, most of the laser energy is absorbed within severalwavelengths travel into the material. From that point, heat istransferred only by conduction from the surface. For that reason, oninitial exposure to the laser beam, a huge thermal gradient is formedbetween the exposed exterior surface and the surface of the mold portionin contact with the lens.

The above objectives are attained by use of a source of electromagneticradiation, preferably a carbon dioxide (CO₂) laser, applied to at leastone of the mold portions and may be split into two beams tosimultaneously heat the back curve of two mold assemblies. It has beenfound through empirical testing that the laser is preferably of about 80Watts per mold assembly at a wavelength of 10.6 μm. The exposure of themold to the laser is between one half and one second.

Lasers of this power range are available both in flowing gas and sealedlaser types. In the preferred embodiment of the laser demoldingapparatus a Laser Photonics model 580 cw/pulse laser was integrated withan optical train as shown in FIG. 25.

Referring to FIG. 25, the input beam 400 is generated by a laser (notshown). The beam first travels through A plano convex lens 412 whichcauses the laser beam to converge. As is readily appreciated by oneskilled in the art, zinc selenide is an appropriate material forconstruction of the lenses and other optical components in an opticaltrain using laser light of the above specified wavelength.

As the beam further diverges it encounters integrator 418 which servesas an internal diffuser. The diffuser serves to scatter the laser lightinternally and provide for a more uniform beam. The beam as originallyproduced by the laser is typically not consistent across the beam inpower distribution. Without a diffuser, this could lead to hot and coldspots on the incident object if a integrator is not used.

Undesirable characteristics can result from under- and overexposure ofthe lens/mold combination to the laser energy. If the energy isnon-uniform across the beam, both effects can be found on the same mold.Because a typical laser beam has a two dimensional Gaussian distributionof energy across the beam, the diffuser is necessary to square off theenergy distribution.

After emerging from integrator 418, the beam is now uniform and weaklyconverging, and is made to be incident upon a beam splitter 420. Thebeam splitter passes half of the beam energy through the splitter andreflects the other half. The half of the beam 422 reflected by splitter420 is reflected by mirrors 24 ultimately causing the beam to strike onelens/mold assembly 39(a). The other half of the beam 428 split by beamsplitter 420, strikes mirror 430 and is reflected to the other lens/moldassembly 39(b).

In this preferred embodiment two mated mold portions containing apolymerized lens therebetween can be simultaneously heated by means ofthe apparatus.

Note that in this instance, the laser utilized between 150 and 200 Wattsso that the laser power incident upon the mold pieces is the preferred,approximate 80 Watts.

Also shown in this arrangement is a helium-neon alignment laser 434 thatis used to assure proper alignment of the optics in the system. Thehelium neon laser 434 produces a beam which is reflected by mirror 438toward the path used by the main laser beam 400. At the intersection ofthe alignment laser beam with the path of the main laser beam, thealignment laser beam encounters beam splitter 439 which places thealignment laser beam in the same path as the main laser beam.

It was found that the preferred method for removing the back moldportion from the front mold portion after heating the back mold portionwith the laser, was to apply a relative tensile force between the moldportions. To apply this tensile force, the front curve mold half is heldin place as illustrated in FIGS. 24(b), 26(a) and 26(b), wherein a pairof thin metal fingers 452,453 are fixably mounted above track rails450,451 and pallet 12(a) to secure the front curve mold half 10 topallet 12(a) during the pry operation. Finger 453 is an inverted Tshaped member and secures the front curve mold half 10 with one flange453(a) of the inverted T, and will engage a second front curve mold half(not shown in FIG. 26(a)) with a second flange 453(b). The second flange453(b) cooperates with a third flange 454 to secure the second frontcurve mold half in position.

As pallet 12 is sequentially advanced through the laser demolder, therails 452-454 sequentially engage each row of mold assemblies 39 tosecure the front curve mold half. The back curve mold half flanges 36are engaged by a pry fixture 448 (diagrammatically illustrated in FIG.24), which engages both sides of flange 36 as the pallet 12 is advancedinto position by the walking beam conveyor block 184. Pallet 12(a) isthen stopped, while pry fixture 448 rotates about axis 456 in thedirection of arrow “F” in FIG. 24 to apply a tensile force to the backcurve mold half 30. The upper part of the pry fixture 448 is capable ofrotation about axis 456 so that after exposure of the back curve moldportion 30 to the laser, the fingers 456,458 pry the back curve moldportion up. The entire assembly is then lifted approximately 10 mm asnoted by arrows “B′-B″” in FIG. 24 to remove the back curve mold partcompletely. It has been found that when the metal fingers 456,458 wereallowed to stop under the flange, and then tilted back approximately18°, the overall quality of the lens removed, and the resultant yieldwas better than currently employed pry techniques which only lift from asingle side, and do not control the axis of the pivot point.

It was determined that such above-described mechanical assistance wasbest supplied just after exposure to the radiation. Although no adverseeffects would be contemplated if there was less time between exposureand mechanical removal, in practical terms the time between exposure andmold separation would be between about 0.2 and about 1.5 seconds.

The preferred arrangement for demolding the back curve mold halves ismore fully illustrated in FIGS. 27(a), 27(b) and 27(c) wherein FIG.27(a) is an elevation view of the apparatus, FIG. 27(b) is a plan viewtaken along section line A-A′ of FIG. 27(a) and FIG. 27(c) is anelevation side view taken along section B-B′ of FIG. 27(a). Asillustrated in FIG. 27(b), pallet 12(a) is on the second of a pluralityof demolding cycles wherein laser beam 400 will deliver intenseelectromagnetic energy from beams 428 and 422 through laser masks 429and 423 to the second row of mold assemblies in pallet 12(a). The firstrow of mold assemblies is being demolded by pry apparatus 448 as waspreviously illustrated and described with respect to FIG. 24. Pryapparatus 448 is rotated by shaft 449 within journal bearing 460 by apair of links 461 and 462 which are illustrated in FIGS. 24 and 27(c).As illustrated in FIG. 27(c), link 462 is pulled in the direction ofarrow “E” by a rack 464 which is driven by a pinion on a stepper motor465. Stepper motor 465 thereby rotates shaft 449 in the directionindicated by the arrow “F” in FIG. 27(c) and FIG. 24 throughapproximately 18° of arc to separate the back curve mold half 30 fromthe front curve mold half 10.

After the pry mechanism 448 and shaft 456 have been rotated, the entireassembly (as mounted on platform 469) is lifted upwardly in thedirection of arrow “G”, about pivot point 466 by means of a slidable cam467 which engages a roller cam follower 468 mounted on pivotableplatform 469. Slidable cam 467 is advanced by a pneumatic or electricdrive motor 470 to raise shaft 449 approximately 10 mm so that theattached pry apparatus 448 may be retracted for disposal of the backcurve mold halves after they have been separated from the mold assembly.

Each of the aforementioned components are mounted on a movable platform471 which is shiftable in both the X and Y direction in order to disposeof the separated back curve mold halves as will be hereinafterdescribed. Once the pry mechanism 448 has separated the back curve moldhalves, and the mechanism has been lifted free of pallet 12(a), platform471 is shifted to the right in the X axis as illustrated by the arrow“H” in FIG. 27(a) by means of a pneumatic drive motor 472. Platform 471is suspended from a stationary tower 473 and mounted for reciprocalmovement along track 474 by means of a column tower 475. Platform 471 isshifted in the direction of arrow “H” in order to place the separatedback curve mold halves over disposal receptacle 476. Simultaneously, ascrapper mechanism 477 is elevated by means of a pneumatic motor 478 toa position parallel with, and just below the surface of pry mechanism448. The shiftable platform 471 is then shifted in the Y axis in thedirection of arrow “J” in FIG. 27(b) to scrape the separated mold curvefrom the pry fixture 448 and cause them to thereby drop into thereceptacle 476 and be vacuated by means of vacuum line 480. Platform 471is shifted in the Y axis by means of pneumatic motor 481 which isfixably mounted to platform 471. Platform 471 is also mounted forreciprocal movement on tower 475 by means of rails 482,483.

Platform 471 is then reciprocated back along the Y axes to its originalposition, and then along the X axes to its original position indirections opposite the arrows “J” and “H” illustrated in FIGS. 27(a)and 27(b). The slidable cam 467 is then withdrawn by drive motor 470 andthe pry mechanism 448 is allowed to lower into position above pallet12(a) while stepper motor 465 returns shaft 449 and the pry mechanism448 to their original orientation. Laser 400 is then energized to heatthe second row of mold assemblies in pallet 12(a), and pallet 12(a) isthen advanced into a pry position by means of reciprocating block member184. Pallet 12(a) is constrained through the demolding apparatus onconveyor 32(f) by means of rails 450 and 451 which prevent verticalmovement and any pitch, yaw or roll of the pallet during the demoldingoperation.

Steam Demolding

The second of the two embodiments for heating the back curve anddemolding the mold assembly uses steam as a high energy heat source. Themold separation apparatus of the second embodiment generally comprisestwo essentially identical steam discharge apparatuses and two associateddemolding assemblies, shown as boundary box 90 in FIG. 8(d) foraccomplishing the simultaneous demolding two parallel lines of aplurality of contact lens molds each containing an ophthalmic lenstherein. The use of two parallel lines increases the throughput of theproduction line. The dual walking beam conveyors 180(a), 180(b) carryindividual pallets, generally illustrated between blocks 184(a), 184(b)for registration within each twelve of the demolding stations.

As illustrated in FIG. 8(d), the dual walking beam conveyors 180(a),180(b) comprises a parallel set of tracks, each track including a pairof tracking ribs for mating with respective grooves 28(a) formed in thepallet 12. The paired set of ribs and respective interlocking grooves28(a) keep the pallet aligned as it is being conveyed within thedemolding apparatus, and, as will be explained in detail below, preventsany vertical movement of the pallet 12 relative to the conveyor. Theblocks 184 provide suitable registration means for precisely locatingthe pallets along the conveyor path for the demolding step.

The demolding assemblies of the mold separation apparatus 90 eachphysically pry the back curve mold half 30 from the front curve half 10of each contact lens mold 11 to physically expose each contact lenssituated in the lens mold for conveyance to a hydration station(illustrated schematically at 89 in FIG. 8(d)) for hydration of thelenses. The prying process occurs under carefully controlled conditions,as will be explained in detail below, so that the back curve half 30will be separated from the front curve half 10 without destroying theintegrity of the lens 8 formed in the lens mold as schematicallyillustrated in FIG. 29. To accomplish this, the mold separationapparatus first prepares the back curve half 30 of each lens moldassembly to enable quick and efficient removal from its respective frontcurve 10 by applying a predetermined amount of heat, preferably in theform of steam, to the back curve half surface.

FIGS. 30(a) through 30(d) illustrate figuratively and in partialcross-section, one demold assembly and a single track 180(a) having apallet 12(a) of mold assemblies thereon. The demold assembly includesreciprocating beam 526 carrying a steam discharge apparatus 528 witheight steam discharge nozzles, two of which are illustrated as 527(a),527(b). In the practice of the invention a separate demolded apparatushaving a second set of nozzles is provided for the second conveyor track180(b). The steam discharge assembly 528 includes eight steam headnozzles connected to a distribution manifold and a steam heat source(not shown), so that steam may be simultaneously applied to each of themold assemblies on the pallet 12(a). To apply heat, the reciprocatingbeam 526 is lowered in the direction of arrow “A” in FIG. 30(a) so thatthe steam head nozzles precisely engage their respective mold assembliesfor applying steam at a carefully controlled temperature and duration.FIG. 30(a) shows only two steam head nozzles 527(a),(b) in engagementwith the mold assemblies on pallet 12(a).

As shown in the general front plan view of FIG. 32, each steamdischarging apparatus 528 generally comprises a plurality of individualnozzle assemblies 527 each mounted in each apparatus 528 at fixedlocations corresponding to the location of each lens mold assembliesseated in the pallet 12. Thus, in the preferred embodiment, there areeight (8) individual nozzle assemblies 527 positioned in each dischargeapparatus.

Each steam discharge apparatus and the nozzle assemblies 527 therein aremounted for reciprocation on a first mounting platform 526 which movesin a plane transverse to conveyors 180(a),(b). The first mountingplatform 526 is caused to vertically reciprocate between a first upperposition illustrated in FIG. 30(d), for a duration of time to allow thepallet 12 carrying the lens mold assemblies to be registered beneath thesteam discharge apparatus 528 and, a second lowered position illustratedin FIG. 30(a) whereby each nozzle assembly 527 is registered in sealingproximity with the surface 34 of the back curve mold portion 30 todirect steam at the surface. The mounting platform 526 is reciprocallydriven by a plurality of screw/nut assemblies driven by a servo motor.

A detailed front elevational view of steam discharging apparatus 528 isillustrated in FIG. 32 and shows a cover assembly 650, a steamdistribution manifold 630 located immediately beneath cover assembly 650for distributing steam from each of two steam intakes to the eightindividual steam nozzle assemblies 527, a condensate manifold 640located immediately beneath steam distribution manifold 630 for removingand regulating the steam pressure applied to the back curve lens moldsurface during steam impingement, and a retaining plate 660 forretaining the individual steam discharge nozzles 527 and two steamintake valves 666(b), 666(a) in the apparatus. The steam intake valve676(b) (and 676(a)) communicates with steam intake pipe 670 via plenum669 to provide pressurized steam to the steam distribution manifold 630.Additionally, a vacuum source (not shown) is connected via suitablepiping 672 to the condensate manifold 640 at input 671 to evacuate thesteam and to regulate the steam pressure applied to the back curve lensmold surface during steam discharge.

A top plan view of the steam distribution manifold 630 of steamdischarge apparatus 528 is illustrated in FIG. 34. As shown in FIG. 34,the steam distribution manifold 630 is provided with a set of eighthollowed bores 660 that each seat a respective steam discharge nozzleassembly 527, and hollowed bores 666(a),(b) that seat respective steamintake valves 676(a), 676(b). Each bore 666(a),(b) is provided with four(4) conduits 668 that extend therefrom and communicate with a centralaxial bore of a respective individual steam discharge nozzle assembly 60to provide steam to each nozzle as will be explained in detail below.

A top plan view of the condensate manifold 640 of steam dischargeapparatus 528 is illustrated in FIG. 35. As shown in FIG. 35, thecondensate manifold 640 is also provided with a set of hollowed bores661 each in axial alignment with the bores 660 of the steam dischargemanifold, and bores 666(c),(d) in axial alignment with the bores666(a),(b) of the steam discharge manifold for accommodating respectivesteam intake valves 676(a), 676(b). Each bore 666(c),(d) is providedwith four (4) conduits 669 that extend therefrom and communicate with ahollowed annular ring of a respective individual steam discharge nozzleassembly 572 for removing steam, as will be explained in detail below.The condensate manifold 640 also defines a channel 665 that connects thevacuum source at input 671 with four of the hollowed bores 661 and thehollowed annular ring of a respective individual steam discharge nozzleassembly 527 when seated therein.

A detailed cross-sectional view of the steam intake valve 676(b)(676(a)) is shown in FIG. 36. Steam at 100° C. is input from a suitablesource, as indicated by the arrow “B” in FIG. 36, through central axialbore 641 and distributed to radial bores 651 that are radially alignedwith conduits 668 of the steam distribution manifold 630 when the valveis seated therein. Thus, steam is distributed from radial bores 651 viathe conduits 668 to each of the individual steam discharge nozzles 527.In an alternative embodiment, the radial bores 651 may be replaced witha hollowed annular bore 651 that communicates with the central bore 641of the steam intake valve and each of the conduits 668 of the steamdistribution manifold. Steam intake valve 676(b) (676(a)) is providedwith a circumferential annular indent 659, such that, when the valve isseated within the discharge apparatus, the indent 659 is aligned withfour of the bores 661 and channel 665 and each of the conduits 669 ofthe condensate manifold 640. When the vacuum is applied to input 671 torelieve the steam pressure within the manifold, the alignment of thepiping 665, indent 659, and conduits 669 assures that the vacuum will besupplied to each of the discharge nozzle assemblies 527. A set ofO-rings 677(a),(b),(c) surrounding the periphery of the steam intakenozzle 666(a) (666(b)) are provided and may be formed EDPM or othersuitable polymer to provide an air-tight seal when seated within therespective manifolds of the discharge apparatus.

A detailed cross-sectional view of an individual nozzle assembly 527 isshown in FIG. 33. The nozzle 527 includes a central axial bore 641 thatforms a discharge orifice 642 located at the bottom 661 of the nozzlefor discharging steam received from the steam distribution manifold 630.As mentioned above with respect to FIG. 34, the central axial bore 641of a respective individual steam discharge nozzle assembly 527 receivespressurized steam from a respective conduit 668 of the steam manifold630. Surrounding the centralized bore 641 is a hollowed annular ring 671having a plurality of bores 643 extending therefrom, two of which643(a), 643(b) are shown in the view of FIG. 33, and which terminate inventing orifices 644(a), 644(b) located concentrically around dischargeorifice 642. The annular ring 671 of each nozzle 527 communicates withbore 661 and a respective conduit 669 of the condensate manifold 640 sothat the vacuum from the vacuum source will be supplied to the bores643(a),(b) of the nozzle 527. During operation, the venting orifices644(a),(b) will simultaneously exhaust the steam when steam is appliedto the back curve lens mold surface through discharge orifice 642.

The physical dimensions of the nozzle assembly 527 are best illustratedin FIG. 33. It comprises essentially a cylindrical upper end 662 havingthe discharge steam input orifice at the top surface thereof. Acylindrical lower end 661 that is smaller in diameter that the upper endhas the discharge orifice 642 and venting orifices 644(a),(b). Thediameter of the nozzle lower end is configured so that the discharge 642and venting orifices 644(a),(b) thereof protrude within the concavesurface 34 of the back curve lens 30 as shown in FIG. 30(a) so as todirect steam directly at the back curve surface. The length of thenozzle that protrudes within the back curve 30 is approximately 1 mm-2.5mm.

Also shown in FIG. 33, surrounding the periphery of the nozzle upper andlower ends, are O-rings 663(a),(b),(c) that may be formed of EDPM orother suitable polymer for providing an air tight seal when the nozzle527 is situated within the hollowed bores of the steam and condensatemanifolds 630,640 of the mounting head assembly 667(a),(b). As describedin greater detail below, when the nozzle 527 is reciprocated to the backcurve mold half 30, the O-ring 663(c) of the lower nozzle end 661 formsa seal with the outer surface 34 of the back curve 10, as illustrated inFIG. 30(a). The seal created between the O-ring 663(c) and the backcurve mold creates a heating chamber between the nozzle and the backcurve, and enables the steam discharged out of central discharge orifice642 to be uniformly distributed along the outer surface 34 of the backcurve mold 30 thereby ensuring an even temperature profile along thatportion of the back curve lens mold surface 34 that is adjacent thecontact lens. Thus, a uniform temperature gradient is created betweenthe back curve lens mold surface 34 and the contact lens 101 to aid inthe separation of the lens mold 30 from the contact lens 101 in the moldseparation apparatus 90. Furthermore, the vacuum exhaust ports644(a)-(d) and the O-rings 663(c) (and the seal created with the backcurve lens mold surface) prevent water condensation from forming on theback curve mold surface. Preferably, steam at 100° C., is discharged forapproximately 2-4 seconds with the venting orifices 664(a),(b)simultaneously removing the steam from the lens mold surface.

As illustrated in FIG. 32, the cover assembly 650 of the steam dischargeapparatus includes bores for accommodating one or more heater cartridges(not shown) which function to keep the nozzles 527 at a temperature thatwill prevent water condensation from forming on the nozzle surface andto assist in preventing water condensation from forming on the backcurve surface 34. Preferably, the temperature of the heater cartridgesare programmed to maintain the temperature of the nozzle at 100° C. orgreater. The cover assembly 650, as illustrated in the front elevationalview of FIG. 32, accommodates two heater cartridge inlets 653(a),(b)with the cartridges therein connected to suitable heater cables656(a),(b).

As shown in FIG. 30(a), during the time the steam discharge nozzles527(a),527(b) thereof discharge steam to the back curve of theindividual lens molds, a set 530(a),530(b) of pry tool are extended bypneumatic drive motors 532,533, as indicated by the arrow “B”, forinsertion between the gaps formed between the respective front and backcurves for each of the four lens molds situated on one side of thepallet 12(a). Likewise, a second set 530(c),530(d) of pry tools areextended by drive motors 534,535 in the direction of the arrow “B′” forinsertion between the gaps formed between the respective front and backcurves of each of the four lens molds situated on the opposite side ofthe pallet 12(a).

Next, as illustrated in FIG. 30(b) after discharging the precisioncontrolled amount of steam, the steam discharge assemblies and the steamnozzles 527 are retracted by a pneumatic drive as illustrated in FIG.30(b) by the arrow “D”, this enables a suction cup assembly unit 590 toalign with the pallet 12(a) as shown. As shown in FIGS. 37-39, eachsuction cup assembly 590 contains eight suction cups (generallyindicated as 585) for precise engagement with a corresponding back curvemold assembly on the pallet when the steam discharge nozzles 527(a),(b)are retracted.

As illustrated in FIGS. 37-39, the suction cup assembly unit 590 shownin FIGS. 30(b)-(d) is mounted on the movable platform 582 and bothreciprocate in both horizontal and vertical directions with respect tothe pallets and mold assemblies. As shown in the detailed view of FIGS.37-39, each suction cup assembly unit 590 comprises a mounting unit 588having legs 589(a),(b) that accommodate suction cups 585 positioned in aone-to-one correspondence with the individual contact lens moldassemblies of a respective pallet. Thus, as illustrated in FIG. 38 eachleg 589(a),(b) has four (4) suction cups 585 that are spaced apart forgripping a respective back curve lens mold. As mentioned generallyabove, each suction cup 585 of the suction cup assembly unit 590(a),(b)vacuum grips a respective back curve 30 of a corresponding lens moldafter the prying operation described in detail below. The mounting unit588 and the legs 589(a),(b) thereof reciprocate along fixed guidedmounts 582 by conventional pneumatic means. The vacuum suction isprovided to each of the plurality of suction cups 585 via conduit 591shown in FIG. 37.

In the preferred embodiment, the pry tools of demolding assembly 90,shown in the diagrammatic elevation views of FIG. 31 are more fullyillustrated in plan view in FIG. 31. As illustrated, two paired sets ofpry tools 530(a)-(d) and 540(a)-(d) each arranged on opposite sides ofrespective pallet conveyors 180(a),180(b). As shown in the FIG. 31, thefirst set of pry tools 530(a),(b) and a second set of pry tools530(c),(d) are located on respective opposite sides of the conveyor180(a) to enable the removal of the back curve lens mold from the frontcurve for each of the eight lens mold assemblies situated in aregistered pallet 12 as represented by the phantom center lines onconveyor 180(a). Each set of tools 530(a),(b) and 530(b),(c) includeupper and lower fingers which separate vertically, one from the other,in a manner to be herewith described in detail. Upper pry tool 530(a)includes a plurality of fingers 516 that form four bights or lensreceiving areas 570, and lower pry tool 530(b) includes a plurality offingers 515 that form four bights or lens receiving areas. Similarly, afirst set of pry tools 540(a),(b) and a second set of pry tools540(c),(d) are located on respective opposite sides of the conveyor180(b) to enable the removal of the back curve lens mold from the frontcurve for each of the eight lens mold assemblies situated in aregistered pallet as represented by the phantom center lines on conveyor180(b). The description that follows is directed to one paired group ofpry tools, e.g., 530(a),(b) and 530(c),(d) but it is understood that thefollowing description applies equally to the other paired group of prytools 540(a)-(d) for the pallet conveyed on conveyor 180(b).

As shown in the detailed side view of FIG. 29 and FIG. 30(a) the topgroup of pry fingers 516 is situated directly above the bottom group ofpry fingers 515 and may be simultaneously inserted into the gap “A”illustrated in FIG. 29 defined between the circumferential flangeportion 36 of the back curve 30 and the circumferential edge portion 18of the front curve 10. The top and bottom fingers 515, 516 of pry tools530(a),(b) are further reciprocable in a vertical direction with respectto each other to perform a prying operation, as will be explained indetail below.

As further illustrated in FIG. 30(a), each set of pry tools 530(a),(b)are inserted in a manner such that fingers 515 thereof of a bottom setof the pry tools anchors the annular flange portion 18 of the frontcurve of the lens mold to the surface of the pallet, and that thefingers 516 of a top set of pry tools by action of a vertical drivemeans will lift beam 526 in the direction of arrow “C” in FIG. 30(c)which will then vertically separate (FIG. 30(c) and (d)) the back curvemold portion 30 of the mold assembly from the front curve mold portion10 without destroying the integrity of the contact lens or either of themold parts.

During the mold separation step illustrated in FIG. 30(c), vacuumsuction for the suction cup assembly 590 is activated, and the top groupof pry tools 530(a),530(c) having a plurality of fingers 516 illustratedin FIG. 31, are caused to separate from the lower group of pry tools530(b),530(d) by a vertical drive means to bias the circumferentialflange of each of the back curve molds 30 away from each of the frontcurves 10 which retain a respective contact lens therein and areanchored by the lower group of pry fingers 515.

As illustrated in FIG. 29, the use of a controlled lifting motionbetween pry fingers 515 and 516 tends to bow the convex portion inwardlywhich will initiate a bilateral separation of the back curve lens, asdenoted at 8(a) and 8(b). This, in turn, initiates a standing wave 8(c)in the material which travels downwardly along the convex surface of theback curve mold half. If the upward movement of the back curve mold halfdoes not exceed the downward propagation rate of the standing wave inthe material, then the back curve will be lifted cleanly without tearingthe lens.

As the back curve is lifted free, it carries with it the HEMA ring 13which may be preferentially retained on the back curve by means ofcorona treatment of the back curve flange 36, or by surfactant treatmentof the front curve flange 18.

Thus, the back curve lens molds 30 are effectively removed from theirrespective front curve lens mold portions and retained by individualsuction cups 585.

Finally, as illustrated in FIG. 30(d), the upper and lower sets of prytools 530(a),530(c) and 530(b),530(d) are retracted laterally inopposite directions indicated by the arrows “E” and “F” in FIG. 30(d),to allow each pallet 12(a) now containing up to eight front curve lensmold portions and a respective contact lens therein, to be conveyed outof the demold assembly by the dual walking beam 180. The suction cups585 retain the corresponding individual back curve mold portions fordisposal. Specifically, the suction cup assembly 590 is retracted to itsoriginal position and the vacuum may be removed therefrom so as torelease the removed back curve lens mold portions. The separated backcurve mold parts are dropped in a bin at the retracted position, andevacuated by a vacuum line (not shown) for disposal.

After the mold assemblies have been separated in the demold apparatus90, each pallet containing the front curve mold halves with an exposedpolymerized contact lens therein, is subsequently transported to ahydration station for hydration and demolding from the front curve lensmold, inspection and packaging. As shown in FIG. 8(d), a dual pusher 202having retractable arms 202 is provided to translate the motion ofpallets 12(a) from each transport carrier of dual walking beam 180 toconveyor 31(d) for transport to the hydration chamber. Prior to transferto the hydration chamber, the integrity of the mold halves contained inthe pallets are checked to determine if any errors have occurred, fore.g., if a back curve mold half was not separated from a correspondingfront curve mold half. The pallet is first clamped between upstreamclamping jaws 207(a),(b) where the pallet is appropriately sensed todetermine if any error is present. If an error indicating that a palletshould be rejected is found, that particular pallet and the contentstherein are transferred from conveyor 31(d) to recirculating conveyor31(e) by pusher assembly 80 as shown in FIG. 8(d). The clamping jaws207(a),(b) release the rejected pallet and the pusher arm 80 pushes thepallet to recirculating conveyor 31(e) where the rejected pallet isconveyed back to the front curve supply conveyor 27. As mentioned above,the contact lens production line facility includes a suction ventapparatus (not shown) for removing the mold assemblies from the rejectedpallet 12(a) while being recirculated back to or while on the frontcurve supply conveyor 27.

If the pallets containing the demolded contact lens assemblies are notrejected, they are alternately clamped by clamping jaws 207(a),(b) andare conveyed as pairs by conveyor 31(d) to transfer pusher assembly 206for transference to the hydration assembly 89. Prior to entering thetransfer pusher 206, the upstream clamping jaws 209(a),(b) temporarilyclamp a pallet to enable a pair of pallets to accumulate therebehind. Ascontrolled by the control means, the clamped pallet are released toenable two pallets 12(a),12(a′) to be forwardly conveyed for alignmentwith reciprocable pusher arm 210 of transfer pusher 206. Drive means 211then enables pusher arm 210 to push the two pallets to a transferapparatus 215, and specifically, a pallet 216 having a flat plateportion 219, that accommodates up to four pallets for transfer of themold assemblies therein to the hydration chamber 89. After the first setof pallets is placed on plate 219, the pusher arm 210 is reciprocated toits original position to receive a second set of two pallets. The pusharm 210 is then enabled to input the second set of two pallets onto theplate 219 of transfer pusher 216 causing the first set of pallets toadvance on the plate. FIG. 8(d) shows the flat plate portion 219 oftransfer pallet 216 containing four pallets that have been pushedthereto by pusher arm 210 two pallets at a time.

As shown in FIG. 8(d), the transfer pallet 216 is mounted forreciprocating horizontal movement on tracks 218(a),(b). In steady stateoperation, suitable drive means (not shown) enables transfer pallet 216and plate 219 carrying four pallets to move across tracks 218(a),(b) inthe direction indicated by arrow “K” in FIG. 19(a) toward the hydrationchamber assembly 89 until it reaches the hydration assembly transferpoint 219(b) where effective transfer of the front curve mold assembliescontaining polymerized contact lenses to the hydration chamber takesplace. After the transfer pallet 216 reaches the transfer point 219(a) avacuum gripping matrix (not shown) of hydration assembly 89 is actuatedto remove up to thirty-two front curve lens mold portions at a time fromthe four pallets on the transfer pallet 216 and transfer them to anappropriate receiving device which transfers the matrix to a de-ionizedwater bath. The transfer pallet 216 and plate 219 carrying empty pallets12(a) now reciprocates along tracks 218(a),(b) in the directionindicated by arrow “M” in FIG. 8(d) back to its original position. Theempty pallets are removed from plate 219 on to the return conveyor 31(f)when the incoming set of new pallets containing front curves are pushedonto the plate by pusher arm 210. Specifically, pusher arm 210 pushes afirst set of new pallets 12(a) on the plate 219 to cause the first setof two empty pallets to exit the plate 219 and engage the conveyor 31(f)for recirculation back to the front curve conveyor 27 pick-up point.Likewise, pusher arm 210 pushes a second set of new pallets 12(a) on theplate 219 which causes the first set of previously positioned newpallets to advance on the plate 219 and enable the second set of twoempty pallets to exit the plate 219 and engage the conveyor 31(f) forrecirculation to the front curve supply pick-up point.

As illustrated in FIG. 8(d) the return conveyor 31(f) connects with thefront curve supply conveyor 27 to return the empty pallets two at a timeto the front curve pick-up point. Suitable pushing means 222 havingreciprocating push arm 224 pushes the pallets onto the supply conveyor27 where they are conveyed to the front curve injection mold assembly 20to receive a new set of eight front curve lens mold halves in the mannerdescribed above.

What is claimed is:
 1. An apparatus for the automated molding of contactlenses from a hydrogel, said apparatus comprising; (a) a transport meansfor transporting a plurality of contact lens molds to and from aplurality of stations, each of said contact lens molds having first andsecond mold parts; (b) a first automated station for receiving aplurality of first mold parts and depositing therein a predeterminedamount of a hydrogel to be cured; (c) a second automated station forreceiving said plurality of first mold parts and assembling each firstmold part with a second mold part to define a contact lens mold cavityand to remove any excess hydrogel from said cavity; (d) a thirdautomated station for curing said hydrogel in said cavity; (e) a fourthautomated station for removing said second mold part from said firstmold part and said molded contact lens, and assembling a plurality ofsaid contact lenses and mold parts in an array for robotic handling; (f)a robotic transfer head, said head facilitating transfer of saidplurality of lenses to a package load station, said robotic transferhead having a plurality of contact lens carriers arranged to correspondto said array, each of said carriers having a convex lens attachmentsurface to receive a contact lens, and a fluid means for introducing afluid between said convex lens attachment surface and said contact lens,said lens being retained thereon during transfer by surface tension; (g)at least one controller for controlling said automated stations and saidrobotic transfer head, said at least one controller positioning saidrobotic transfer head and initiating the introduction of said fluid bysaid fluid means to transfer said contact lenses to said packages.
 2. Anapparatus as claimed in claim 1 which further includes enclosure meansfor surrounding said first and second automated stations with an inertatmosphere.
 3. A method of automatically molding contact lenses from apolymerizable monomer or monomer mixture, said method comprising; (a)transporting a plurality of first and second mold parts for theproduction of soft contact lens blanks to and from a plurality ofautomated stations, said plurality arranged in an array; (b) depositinga predetermined amount of a polymerizable monomer or monomer mixture insaid first mold part, and then; (c) assembling each first mold part witha second mold part with the monomer or monomer mixture there between todefine a contact lens mold cavity and to remove any excess monomer fromsaid cavity and then; (d) polymerizing said monomer or monomer mixturein said cavity with radiant energy; and then (e) automatically demoldingeach of said contact lenses by removing said second mold part and anyexcess monomer from said first mold part and said molded contact lens;and then (f) automatically transferring said plurality of lenses with arobotic transfer head to a plurality of packages at a package loadstation, said robotic transfer head having a plurality of contact lenscarriers, with each of said carriers having a convex lens attachmentsurface to receive a contact lens, said lens being retained thereonduring transfer by surface tension; (g) controlling said method stepsand said robotic transfer head with at least one controller, saidcontrolling step positioning said robotic transfer head and initiatingthe introduction of said fluid by said fluid means to transfer saidcontact lenses to said packages.
 4. A method as claimed in claim 3 whichfurther includes the step of transporting said mold parts between saidautomated stations in an inert atmosphere to prevent absorption ofoxygen thereon.
 5. A method as claimed in claim 3 which further includesthe step of molding sets of said first and second mold parts at atemperature of at least 450 degrees F. within a cycle time of 3 to 12seconds.
 6. A method as claimed in claim 5 wherein the step oftransferring said molded sets from said molding step to said inertatmosphere occurs within 15 seconds of the completion of said moldingstep.
 7. A method as claimed in claim 3 wherein said method furtherincludes the step of clamping said mold parts together in said assemblystep to firmly displace said excess hydrogel from said mold cavity.
 8. Amethod as claimed in claim 3 wherein said method further includes thestep of filling each package with a precise dose of buffered salinesolution.
 9. A method as claimed in claim 3 wherein said method furtherincludes the step of heat sealing a plurality of said packages to asingle foil laminate so that final lens equilibrium is accomplishedafter the lens has been packaged and sealed.
 10. A method as claimed inclaim 3 wherein said method further includes the step of automaticallyinspecting each lens by directing a light pulse through each lens to apixel array to generate an electrical signal which is processed todetermine if the lens is acceptable and to generate a signal if saidlens is defective.
 11. An apparatus for the automated molding of contactlenses as claimed in claim 1 wherein said contact lenses are arranged inan array, and said contact lens carriers are arranged in a correspondingarray to facilitate the transfer of contact lenses to said plurality ofcontact lens carriers.
 12. An apparatus for the automated molding ofcontact lenses as claimed in claim 11 wherein said packages at saidpackage load station are also arranged in a corresponding array tofacilitate the transfer of contact lenses to a plurality of packages atsaid package load station.
 13. An apparatus for the automated molding ofcontact lenses as claimed in claim 12 wherein said contact lenses arearranged in an array of concave carriers, and are wetted with a solutionhaving a small amount of surfactant therein prior to transfer to saidplurality of contact lens carriers.
 14. An apparatus for the automatedmolding of contact lenses as claimed in claim 13 wherein the surfactantwets the surface of the contact lens carrier to promote surface tensionadhesion of the contact lenses to the contact lens carriers.
 15. Anapparatus for the automated molding of contact lenses as claimed inclaim 1 wherein said apparatus further includes a package dosing stationto fill each of a plurality of packages at said package load stationwith a precise dose of buffered saline solution.
 16. An apparatus forthe automated molding of contact lenses as claimed in claim 15 whereinsaid apparatus further includes a package sealing station to heat seal aplurality of said packages to a foil laminate so that final lensequilibrium is accomplished after the lens has been packaged and sealed.17. An apparatus for the automated molding of contact lenses as claimedin claim 1, wherein said apparatus further includes a molding stationfor injection molding fully degassed first and second mold parts for theproduction of soft contact lenses and a transport means for receivingsaid mold parts from said molding station and transporting said moldparts in a low oxygen environment to and from a plurality of automatedstations.
 18. An apparatus for the automated molding of contact lensesas claimed in claim 17 wherein said molding station injection molds saidfirst and second mold parts at a temperature of at least 450 degrees F.over a cycle of 3 to 12 seconds.
 19. An apparatus for the automatedmolding of contact lenses as claimed in claim 18 which further includesrobotic means for transfer of said mold parts from said molding stationto said transport means and said low oxygen environment within 15seconds or less.
 20. An apparatus for the automated molding of contactlenses as claimed in claim 1 wherein said second automated stationfurther includes a first clamping means for clamping said mold partstogether under vacuum to displace any excess hydrogel and to firmly seatand align the mold parts.
 21. An apparatus for the automated molding ofcontact lenses as claimed in claim 17 wherein said transport includes aplurality of pallets for receiving said mold parts, each palletincluding a perimeter seal area to cooperate with a perimeter sealformed at said second automated station to enable assembly of said moldparts under vacuum.
 22. An apparatus for the automated molding ofcontact lenses as claimed in claim 21 wherein said transport meansfurther includes separate pallets for said second mold parts, whereinsaid pallets having first mold parts are interleaved with pallets havingsecond mold parts.
 23. An apparatus for the automated molding of contactlenses as claimed in claim 22 wherein said second automated stationcycles between pallets, picking up second mold parts from a pallet in afirst cycle, and depositing said second mold parts on said first moldparts in a second pallet during a second cycle to assemble said mold.24. An apparatus for the automated molding of contact lenses as claimedin claim 23 wherein said second automated stations further comprises:(i) a housing member for surrounding aligned first and second mold partsto thereby enable a vacuum to be drawn around said parts; and (ii) saidsecond automated station having a reciprocating means for reciprocatingsaid second mold parts along a reciprocating axis to clamp said secondmold parts against said first mold part with a predetermined pressurewhile said vacuum remains drawn.
 25. An apparatus for the automatedmolding of contact lenses as claimed in claim 17 in which each of saidmold parts also has a flange and a generally triangular tab situated ina plane normal to and extending from said flange, said mold parts havinga thinness sufficient to transmit heat therethrough rapidly and rigidityeffective to withstand prying forces applied to separate said moldparts.
 26. An apparatus for the automated molding of contact lenses asclaimed in claim 25 wherein the surface of each mold part is essentiallyfree of oxygen when assembled.
 27. An apparatus for the automatedmolding of contact lenses as claimed in claim 26 wherein saidthermoplastic polymer is polystyrene.
 28. An apparatus for the automatedmolding of contact lenses as claimed in claim 1 wherein said fourthautomated station is adapted for demolding a mold assembly having afirst and second flange formed on each of said first and second moldparts, said station further including: (a) heating means for applyingheat to said second mold part to form a temperature gradient betweensaid second mold part and the contact lens; and, (b) pry means fordemolding said lens, said pry means inserted between said flanges ofsaid first and said second mold parts of said mold assembly, said prymeans including a first and second set of pry fingers for biasing saidsecond mold part upwardly at a predetermined force with respect to saidfirst mold part to remove said second mold part therefrom.
 29. Anapparatus for the automated molding of contact lenses as claimed inclaim 28 wherein said pry means lifts said back mold part from saidfront mold part at a predetermined time after application of said heat.30. An apparatus for the automated molding of contact lenses as claimedin claim 29 wherein said pry means includes means for displacing saidfirst set of pry fingers in a substantially vertical direction whilesaid second set of pry fingers anchors said first mold parts, therebyseparating said mold parts.
 31. An apparatus for the automated moldingof contact lenses as claimed in claim 30 wherein said first and secondset of pry fingers are extensible from a first retracted position to asecond extended position between said flanges of said first and saidsecond mold parts of said mold assembly.
 32. An apparatus for theautomated molding of contact lenses as claimed in claim 31 wherein saidpry means are inserted between said first and second flanges of saidfirst and second mold parts of said contact lens mold assembly whilesaid heat is applied to each second mold part by a heating means.